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Scott AI. Very-Long-Chain Fatty Acids Quantification by Gas-Chromatography Mass Spectrometry. Methods Mol Biol 2022; 2546:501-508. [PMID: 36127617 DOI: 10.1007/978-1-0716-2565-1_45] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Abnormal accumulation of very-long-chain fatty acids (VLCFAs), defined as molecules with greater than 22 carbons, and branched-chain fatty acids, pristanic and phytanic acids, is characteristic of inborn errors of peroxisomal biogenesis or function. X-linked adrenoleukodystrophy, Zellweger spectrum disorders, rhizomelic chondrodysplasia punctata, and Refsum syndrome can be diagnosed biochemically by quantitation of these metabolites in plasma. Ratios of C24/C22 and C26/C22 can help improve detection of X-linked adrenoleukodystrophy. Analysis using gas-chromatography mass spectrometry (GC/MS) after acid/base hydrolysis, organic solvent extraction, and derivatization is an established method for clinical diagnostics. This chapter describes detailed steps to process plasma samples for GC/MS analysis.
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Affiliation(s)
- Anna I Scott
- Department of Laboratories, Seattle Children's Hospital, Seattle, WA, USA. .,Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, USA.
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Zhang T, Duong P, Dayuha R, Collins CJ, Beckman E, Thies J, Chang I, Lam C, Sun A, Scott AI, Thompson J, Singh A, Khaledi H, Gelb MH, Hahn SH. A rapid and non-invasive proteomic analysis using DBS and buccal swab for multiplexed second-tier screening of Pompe disease and Mucopolysaccharidosis type I. Mol Genet Metab 2022; 136:296-305. [PMID: 35787971 PMCID: PMC10387444 DOI: 10.1016/j.ymgme.2022.06.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Revised: 06/21/2022] [Accepted: 06/23/2022] [Indexed: 11/19/2022]
Abstract
PURPOSE Current newborn screening programs for Pompe disease (PD) and mucopolysaccharidosis type I (MPS I) suffer from a high false positive rate and long turnaround time for clinical follow up. This study aimed to develop a novel proteomics-based assay for rapid and accurate second-tier screening of PD and MPS I. A fast turnaround assay would enable the identification of severe cases who need immediate clinical follow up and treatment. METHODS We developed an immunocapture coupled with mass spectrometry-based proteomics (Immuno-SRM) assay to quantify GAA and IDUA proteins in dried blood spots (DBS) and buccal swabs. Sensitivity, linearity, reproducibility, and protein concentration range in healthy control samples were determined. Clinical performance was evaluated in known PD and MPS I patients as well as pseudodeficiency and carrier cases. RESULTS Using three 3.2 mm punches (~13.1 μL of blood) of DBS, the assay showed reproducible and sensitive quantification of GAA and IDUA. Both proteins can also be quantified in buccal swabs with high reproducibility and sensitivity. Infantile onset Pompe disease (IOPD) and severe MPS I cases are readily identifiable due to the absence of GAA and IDUA, respectively. In addition, late onset Pompe disease (LOPD) and attenuated MPS I patients showed much reduced levels of the target protein. By contrast, pseudodeficiency and carrier cases exhibited significant higher target protein levels compared to true patients. CONCLUSION Direct quantification of endogenous GAA and IDUA peptides in DBS by Immuno-SRM can be used for second-tier screening to rapidly identify severe PD and MPS I patients with a turnaround time of <1 week. Such patients could benefit from immediate clinical follow up and possibly earlier treatment.
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Affiliation(s)
- Tong Zhang
- Seattle Children's Research Institute, Seattle, WA, United States of America
| | - Phi Duong
- Seattle Children's Research Institute, Seattle, WA, United States of America
| | - Remwilyn Dayuha
- Seattle Children's Research Institute, Seattle, WA, United States of America
| | | | - Erika Beckman
- Division of Genetic Medicine, Seattle Children's Hospital, Seattle, WA, United States of America
| | - Jenny Thies
- Division of Genetic Medicine, Seattle Children's Hospital, Seattle, WA, United States of America
| | - Irene Chang
- Biochemical Genetics Clinic, Seattle Children's Hospital, Seattle, WA, United States of America; Department of Pediatrics, Division of Genetic Medicine, University of Washington School of Medicine, Seattle, WA, United States of America
| | - Christina Lam
- Biochemical Genetics Clinic, Seattle Children's Hospital, Seattle, WA, United States of America; Department of Pediatrics, Division of Genetic Medicine, University of Washington School of Medicine, Seattle, WA, United States of America
| | - Angela Sun
- Biochemical Genetics Clinic, Seattle Children's Hospital, Seattle, WA, United States of America; Department of Pediatrics, Division of Genetic Medicine, University of Washington School of Medicine, Seattle, WA, United States of America
| | - Anna I Scott
- Department of Laboratory, Seattle Children's Hospital, Seattle, WA, United States of America
| | - John Thompson
- WA State Department of Health, Seattle, WA, United States of America
| | - Aranjeet Singh
- WA State Department of Health, Seattle, WA, United States of America
| | - Hamid Khaledi
- Department of Chemistry, University of Washington, Seattle, WA, United States of America
| | - Michael H Gelb
- Department of Chemistry, University of Washington, Seattle, WA, United States of America
| | - Si Houn Hahn
- Seattle Children's Research Institute, Seattle, WA, United States of America; Biochemical Genetics Clinic, Seattle Children's Hospital, Seattle, WA, United States of America; Department of Pediatrics, Division of Genetic Medicine, University of Washington School of Medicine, Seattle, WA, United States of America.
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3
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Johnson JO, Chia R, Miller DE, Li R, Kumaran R, Abramzon Y, Alahmady N, Renton AE, Topp SD, Gibbs JR, Cookson MR, Sabir MS, Dalgard CL, Troakes C, Jones AR, Shatunov A, Iacoangeli A, Al Khleifat A, Ticozzi N, Silani V, Gellera C, Blair IP, Dobson-Stone C, Kwok JB, Bonkowski ES, Palvadeau R, Tienari PJ, Morrison KE, Shaw PJ, Al-Chalabi A, Brown RH, Calvo A, Mora G, Al-Saif H, Gotkine M, Leigh F, Chang IJ, Perlman SJ, Glass I, Scott AI, Shaw CE, Basak AN, Landers JE, Chiò A, Crawford TO, Smith BN, Traynor BJ. Association of Variants in the SPTLC1 Gene With Juvenile Amyotrophic Lateral Sclerosis. JAMA Neurol 2021; 78:1236-1248. [PMID: 34459874 PMCID: PMC8406220 DOI: 10.1001/jamaneurol.2021.2598] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Accepted: 05/27/2021] [Indexed: 02/06/2023]
Abstract
Importance Juvenile amyotrophic lateral sclerosis (ALS) is a rare form of ALS characterized by age of symptom onset less than 25 years and a variable presentation. Objective To identify the genetic variants associated with juvenile ALS. Design, Setting, and Participants In this multicenter family-based genetic study, trio whole-exome sequencing was performed to identify the disease-associated gene in a case series of unrelated patients diagnosed with juvenile ALS and severe growth retardation. The patients and their family members were enrolled at academic hospitals and a government research facility between March 1, 2016, and March 13, 2020, and were observed until October 1, 2020. Whole-exome sequencing was also performed in a series of patients with juvenile ALS. A total of 66 patients with juvenile ALS and 6258 adult patients with ALS participated in the study. Patients were selected for the study based on their diagnosis, and all eligible participants were enrolled in the study. None of the participants had a family history of neurological disorders, suggesting de novo variants as the underlying genetic mechanism. Main Outcomes and Measures De novo variants present only in the index case and not in unaffected family members. Results Trio whole-exome sequencing was performed in 3 patients diagnosed with juvenile ALS and their parents. An additional 63 patients with juvenile ALS and 6258 adult patients with ALS were subsequently screened for variants in the SPTLC1 gene. De novo variants in SPTLC1 (p.Ala20Ser in 2 patients and p.Ser331Tyr in 1 patient) were identified in 3 unrelated patients diagnosed with juvenile ALS and failure to thrive. A fourth variant (p.Leu39del) was identified in a patient with juvenile ALS where parental DNA was unavailable. Variants in this gene have been previously shown to be associated with autosomal-dominant hereditary sensory autonomic neuropathy, type 1A, by disrupting an essential enzyme complex in the sphingolipid synthesis pathway. Conclusions and Relevance These data broaden the phenotype associated with SPTLC1 and suggest that patients presenting with juvenile ALS should be screened for variants in this gene.
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Affiliation(s)
- Janel O. Johnson
- Neuromuscular Diseases Research Section, Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, Maryland
| | - Ruth Chia
- Neuromuscular Diseases Research Section, Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, Maryland
| | - Danny E. Miller
- Division of Medical Genetics, Department of Medicine, University of Washington, Seattle
- Department of Pediatrics, Division of Genetic Medicine, Seattle Children’s Hospital, University of Washington, Seattle
| | - Rachel Li
- Department of Pediatrics, Children’s Hospital of Richmond at VCU, Richmond, Virginia
| | - Ravindran Kumaran
- Cell Biology and Gene Expression Section, Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, Maryland
| | - Yevgeniya Abramzon
- Neuromuscular Diseases Research Section, Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, Maryland
- Reta Lila Weston Institute, UCL Queen Square Institute of Neurology, University College London, London, United Kingdom
| | - Nada Alahmady
- Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, United Kingdom
- Department of Biology, Imam Abdulrahman bin Faisal University, Dammam, Saudi Arabia
| | - Alan E. Renton
- Neuromuscular Diseases Research Section, Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, Maryland
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York
- Ronald M. Loeb Center for Alzheimer’s Disease, Icahn School of Medicine at Mount Sinai, New York, New York
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Simon D. Topp
- Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, United Kingdom
- UK Dementia Research Institute at King’s College London, London, United Kingdom
| | - J. Raphael Gibbs
- Computational Biology Group, Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, Maryland
| | - Mark R. Cookson
- Reta Lila Weston Institute, UCL Queen Square Institute of Neurology, University College London, London, United Kingdom
| | - Marya S. Sabir
- Neurodegenerative Diseases Research Unit, Laboratory of Neurogenetics, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland
| | - Clifton L. Dalgard
- Department of Anatomy, Physiology & Genetics, Uniformed Services University of the Health Sciences, Bethesda, Maryland
- The American Genome Center, Collaborative Health Initiative Research Program, Uniformed Services University of the Health Sciences, Bethesda, Maryland
| | - Claire Troakes
- Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, United Kingdom
| | - Ashley R. Jones
- Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, United Kingdom
| | - Aleksey Shatunov
- Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, United Kingdom
| | - Alfredo Iacoangeli
- Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, United Kingdom
| | - Ahmad Al Khleifat
- Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, United Kingdom
| | - Nicola Ticozzi
- Istituto Auxologico Italiano, IRCCS, Department of Neurology–Stroke Unit and Laboratory of Neuroscience, Milan, Italy
- Department of Pathophysiology and Transplantation, “Dino Ferrari” Center, Università degli Studi di Milano, Milan, Italy
| | - Vincenzo Silani
- Istituto Auxologico Italiano, IRCCS, Department of Neurology–Stroke Unit and Laboratory of Neuroscience, Milan, Italy
- Department of Pathophysiology and Transplantation, “Dino Ferrari” Center, Università degli Studi di Milano, Milan, Italy
| | - Cinzia Gellera
- Unit of Genetics of Neurodegenerative and Metabolic Diseases, Fondazione IRCCS Istituto Neurologico ‘Carlo Besta,’ Milan, Italy
| | - Ian P. Blair
- Centre for Motor Neuron Disease Research, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Macquarie University, Sydney, Australia
| | - Carol Dobson-Stone
- The University of Sydney, Brain and Mind Centre and School of Medical Sciences, Faculty of Medicine and Health, Camperdown, Australia
- School of Medical Sciences, University of New South Wales, Kensington, Australia
| | - John B. Kwok
- The University of Sydney, Brain and Mind Centre and School of Medical Sciences, Faculty of Medicine and Health, Camperdown, Australia
- School of Medical Sciences, University of New South Wales, Kensington, Australia
| | - Emily S. Bonkowski
- Department of Pediatrics, Division of Genetic Medicine, Seattle Children’s Hospital, University of Washington, Seattle
| | - Robin Palvadeau
- Suna and Inan Kırac Foundation, Neurodegeneration Research Laboratory, KUTTAM, School of Medicine, Koc University, Istanbul, Turkey
| | - Pentti J. Tienari
- Department of Neurology, Helsinki University Hospital and Translational Immunology Programme, Biomedicum, University of Helsinki, Helsinki, Finland
| | - Karen E. Morrison
- Faculty of Medicine, Health and Life Sciences, Queen’s University Belfast, Belfast, United Kingdom
| | - Pamela J. Shaw
- Sheffield Institute for Translational Neuroscience, Department of Neuroscience, University of Sheffield, Sheffield, United Kingdom
| | - Ammar Al-Chalabi
- Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, United Kingdom
- Department of Neurology, King’s College Hospital, London, United Kingdom
| | - Robert H. Brown
- Department of Neurology, University of Massachusetts Medical School, Worcester
| | - Andrea Calvo
- ALS Center, ‘Rita Levi Montalcini’ Department of Neuroscience, University of Turin, Turin, Italy
| | | | - Hind Al-Saif
- Department of Neurology, Children’s Hospital of Richmond at VCU, Richmond, Virginia
| | - Marc Gotkine
- Department of Neurology, The Agnes Ginges Center for Human Neurogenetics, Hadassah Medical Organization and Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Fawn Leigh
- Department of Neurology, Seattle Children’s Hospital, University of Washington, Seattle
| | - Irene J. Chang
- Division of Medical Genetics, Department of Medicine, University of Washington, Seattle
| | - Seth J. Perlman
- Department of Neurology, Seattle Children’s Hospital, University of Washington, Seattle
| | - Ian Glass
- Division of Medical Genetics, Department of Medicine, University of Washington, Seattle
- Department of Pediatrics, Division of Genetic Medicine, Seattle Children’s Hospital, University of Washington, Seattle
| | - Anna I. Scott
- Department of Laboratories, Seattle Children’s Hospital, Seattle, Washington
- Department of Laboratory Medicine, University of Washington, Seattle
| | - Christopher E. Shaw
- Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, United Kingdom
- UK Dementia Research Institute at King’s College London, London, United Kingdom
| | - A. Nazli Basak
- Suna and Inan Kırac Foundation, Neurodegeneration Research Laboratory, KUTTAM, School of Medicine, Koc University, Istanbul, Turkey
| | - John E. Landers
- Department of Neurology, University of Massachusetts Medical School, Worcester
| | - Adriano Chiò
- ALS Center, ‘Rita Levi Montalcini’ Department of Neuroscience, University of Turin, Turin, Italy
- Neurology 1, AOU Città della Salute e della Scienza, Turin, Italy
| | - Thomas O. Crawford
- Department of Neurology, Johns Hopkins University, Baltimore, Maryland
- Department of Pediatrics, Johns Hopkins University, Baltimore, Maryland
| | - Bradley N. Smith
- Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, United Kingdom
| | - Bryan J. Traynor
- Neuromuscular Diseases Research Section, Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, Maryland
- Reta Lila Weston Institute, UCL Queen Square Institute of Neurology, University College London, London, United Kingdom
- Department of Neurology, Johns Hopkins University, Baltimore, Maryland
- National Institute of Neurological Disorders and Stroke, Bethesda, Maryland
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Kelley J, Sullivan E, Norris M, Sullivan S, Parietti J, Kellogg K, Scott AI. Carnitine deficiency among hospitalized pediatric patients: A retrospective study of critically ill patients receiving extracorporeal membrane oxygenation therapy. JPEN J Parenter Enteral Nutr 2021; 45:1663-1672. [PMID: 34415080 PMCID: PMC9293107 DOI: 10.1002/jpen.2255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Background The metabolic demands associated with critical illness place patients at risk for nutrition deficits. Carnitine is a small molecule essential for fatty acid oxidation and gluconeogenesis. Secondary carnitine deficiency can have clinically significant complications and has been observed anecdotally in patients receiving extracorporeal membrane oxygenation (ECMO) therapy at our institution. Guidelines for monitoring and supplementing carnitine are lacking. This retrospective study determined whether critically ill pediatric patients receiving ECMO have an increased risk of carnitine deficiency. Methods Acylcarnitine analysis was performed on residual specimens from patients who received ECMO therapy. The control data were a convenience sample gathered by chart review of patients who had been tested for carnitine during a hospitalization. Results Acylcarnitines were measured in 217 non‐ECMO patients and 81 ECMO patients. Carnitine deficiency, based on age‐specific reference ranges, was observed in 41% of ECMO cases compared with 21% of non‐ECMO cases. Multivariable analysis of age‐matched patients identified that the odds of carnitine deficiency were significantly lower among patients on the floor compared with ECMO patients (odds ratio, 0.21; 95% CI, 0.10–0.44). Age‐specific frequency of qualitative carnitine deficiency ranged from 15% (patients >5 years old) to 56% (patients 1 week to 1 month old) in ECMO patients and 15% (patients >5 years old) to 34% (patients 1–5 years old) in non‐ECMO patients. Conclusion In this study, ECMO patients were carnitine deficient more frequently compared with other inpatients, with the highest rates of deficiency among ECMO patients between 1 week and 1 month old.
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Affiliation(s)
- Jenna Kelley
- Department of Nutrition Services, Seattle Children's Hospital, Seattle, Washington, USA
| | - Erin Sullivan
- Biostatistics, Epidemiology, and Analytics for Research, Seattle Children's Hospital, Seattle, Washington, USA
| | - Marie Norris
- Department of Nutrition Services, Seattle Children's Hospital, Seattle, Washington, USA.,Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah, USA
| | - Sarah Sullivan
- Department of Nutrition Services, Seattle Children's Hospital, Seattle, Washington, USA
| | - Jennifer Parietti
- Department of Nutrition Services, Seattle Children's Hospital, Seattle, Washington, USA
| | - Kimberly Kellogg
- Department of Nutrition Services, Seattle Children's Hospital, Seattle, Washington, USA
| | - Anna I Scott
- Department of Laboratories, Seattle Children's Hospital, Seattle, Washington, USA.,Department of Laboratory Medicine and Pathology, University of Washington, Seattle, Washington, USA
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Guenzel AJ, Hall PL, Scott AI, Lam C, Chang IJ, Thies J, Ferreira CR, Pichurin P, Laxen W, Raymond K, Gavrilov DK, Oglesbee D, Rinaldo P, Matern D, Tortorelli S. The low excretor phenotype of glutaric acidemia type I is a source of false negative newborn screening results and challenging diagnoses. JIMD Rep 2021; 60:67-74. [PMID: 34258142 PMCID: PMC8260482 DOI: 10.1002/jmd2.12217] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Revised: 03/23/2021] [Accepted: 03/25/2021] [Indexed: 01/23/2023] Open
Abstract
BACKGROUND Glutaric acidemia type I (GA1) is an organic acidemia that is often unrecognized in the newborn period until patients suffer an acute encephalopathic crisis, which can be mistaken for nonaccidental trauma. Presymptomatic identification of GA1 patients is possible by newborn screening (NBS). However, the biochemical "low-excretor" (LE) phenotype with nearly normal levels of disease metabolites can be overlooked, which may result in untreated disease and irreversible neurological sequelae. The LE phenotype is also a potential source of false negative (FN) NBS results that merits further investigation. METHODS Samples from six LE GA1 patients were analyzed by biochemical and molecular methods and newborn screen outcomes were retrospectively investigated. RESULTS Five LE GA1 patients were identified that had normal NBS results and three of these presented clinically with GA1 symptoms. One additional symptomatic patient was identified who did not undergo screening. Semiquantitative urine organic acid analysis was consistent with a GA1 diagnosis in two (33%) of the six patients, while plasma glutarylcarnitine was elevated in four (67%) of the six and urine glutarylcarnitine was elevated in four (80%) of five patients. Five GCDH variants were identified in these patients; three of which have not been previously linked to the biochemical LE phenotype. CONCLUSIONS The data presented here raise awareness of potential FN NBS results for LE GA1 patients. The LE phenotype is not protective against adverse clinical outcomes, and the possibility of FN NBS results calls for high vigilance amongst clinicians, even in the setting of a normal NBS result.
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Affiliation(s)
- Adam J. Guenzel
- Biochemical Genetics Laboratory, Mayo ClinicRochesterMinnesotaUSA
| | | | - Anna I. Scott
- Biochemical Genetics LaboratorySeattle Children's HospitalSeattleWashingtonUSA
| | - Christina Lam
- Division of Genetic Medicine, Department of PediatricsUniversity of Washington and Seattle Children's HospitalSeattleWashingtonUSA
| | - Irene J. Chang
- Division of Genetic Medicine, Department of PediatricsUniversity of Washington and Seattle Children's HospitalSeattleWashingtonUSA
| | - Jenny Thies
- Division of Genetic Medicine, Department of PediatricsUniversity of Washington and Seattle Children's HospitalSeattleWashingtonUSA
| | | | - Pavel Pichurin
- Division of Clinical GenomicsMayo ClinicRochesterMinnesotaUSA
| | - William Laxen
- Biochemical Genetics Laboratory, Mayo ClinicRochesterMinnesotaUSA
| | - Kimiyo Raymond
- Biochemical Genetics Laboratory, Mayo ClinicRochesterMinnesotaUSA
| | | | - Devin Oglesbee
- Biochemical Genetics Laboratory, Mayo ClinicRochesterMinnesotaUSA
| | - Piero Rinaldo
- Biochemical Genetics Laboratory, Mayo ClinicRochesterMinnesotaUSA
| | - Dietrich Matern
- Biochemical Genetics Laboratory, Mayo ClinicRochesterMinnesotaUSA
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Liao HC, Jack R, Scott AI. Galactocerebrosidase activity by liquid-chromatography tandem mass spectrometry for clinical diagnosis of Krabbe disease. Clin Chim Acta 2021; 519:300-305. [PMID: 34015306 DOI: 10.1016/j.cca.2021.05.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Revised: 05/10/2021] [Accepted: 05/13/2021] [Indexed: 10/21/2022]
Abstract
BACKGROUND Deficiency of galactosylcerebrosidase (GALC) causes Krabbe disease. Historically, a diagnosis is made by measuring GALC enzymatic activity with a radioisotope assay. To improve the workflow and performance, we developed and clinically validated a leukocyte enzymatic assay using liquid chromatography tandem mass spectrometry (LC-MS/MS). MATERIALS Extracted cell lysates were quantified and incubated with commercially available multiplexed substrates and internal standards. Liquid-liquid extraction was performed, and pre-analytical and analytical variability were evaluated and validated following clinical laboratory regulation guidelines. RESULTS Enzymatic reaction products were resolved from substrate breakdown products by a 3.5-minute column separation. Intra- and inter- assay imprecision were less than 15%. No matrix effects or carryover were observed. ACD anticoagulant tubes provide the best sample stability. Detection of product was linear with an R2 of 0.99. Small differences in GALC activity were measurable near the anticipated disease range. Confirmed cases of Krabbe disease were well differentiated from carriers and non-Krabbe individuals (normal reference range). CONCLUSION An LC-MS/MS assay was developed, which can measure trace residual GALC activity in leukocytes and aid in the diagnosis of Krabbe disease. The multiplexed mixture allows for built-in sample quality control and enables a streamlined workflow for evaluation of multiple lysosomal storage diseases.
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Affiliation(s)
- Hsuan-Chieh Liao
- University of Washington, Department of Laboratory Medicine and Pathology, Seattle, WA, United States; Seattle Children's Hospital, Department of Laboratories, Seattle, WA, United States
| | - Rhona Jack
- University of Washington, Department of Laboratory Medicine and Pathology, Seattle, WA, United States; Seattle Children's Hospital, Department of Laboratories, Seattle, WA, United States
| | - Anna I Scott
- University of Washington, Department of Laboratory Medicine and Pathology, Seattle, WA, United States; Seattle Children's Hospital, Department of Laboratories, Seattle, WA, United States.
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Norris MK, Scott AI, Sullivan S, Chang IJ, Lam C, Sun A, Hahn S, Thies JM, Gunnarson M, McKean KN, Merritt JL. Tutorial: Triheptanoin and Nutrition Management for Treatment of Long-Chain Fatty Acid Oxidation Disorders. JPEN J Parenter Enteral Nutr 2020; 45:230-238. [PMID: 33085788 DOI: 10.1002/jpen.2034] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 09/22/2020] [Accepted: 10/14/2020] [Indexed: 12/14/2022]
Abstract
BACKGROUND Patients with severe long-chain fatty acid oxidation disorders (LC-FAODs) experience serious morbidity and mortality despite traditional dietary management including medium-chain triglyceride (MCT)-supplemented, low-fat diets. Triheptanoin is a triglyceride oil that is broken down to acetyl-coenzyme A (CoA) and propionyl-CoA, which replenishes deficient tricarboxylic acid cycle intermediates. We report the complex medical and nutrition management of triheptanoin therapy initiated emergently for 3 patients with LC-FAOD. METHODS Triheptanoin (Ultragenyx Pharmaceutical, Inc, Novato, CA, USA) was administered to 3 patients with LC-FAOD on a compassionate-use basis. Triheptanoin was mixed with non-MCT-containing low-fat formula. Patients were closely followed with regular cardiac and laboratory monitoring. RESULTS Cardiac ejection fraction normalized after triheptanoin initiation. Patients experienced fewer hospitalizations related to metabolic crises while on triheptanoin. Patient 1 has tolerated oral administration without difficulty since birth. Patients 2 and 3 experienced increased diarrhea. Recurrent breakdown of the silicone gastrostomy tube occurred in patient 3, whereas the polyurethane nasogastric tube for patient 2 remained intact. Patient 3 experiences recurrent episodes of elevated creatine kinase levels and muscle weakness associated with illness. Patient 3 had chronically elevated C10-acylcarnitines while on MCT supplementation, which normalized after initiation of triheptanoin and discontinuation of MCT oil. CONCLUSIONS Triheptanoin can ameliorate acute cardiomyopathy and increase survival in patients with severe LC-FAOD. Substituting triheptanoin for traditional MCT-based treatment improves clinical outcomes. MCT oil might be less effective in carnitine-acylcarnitine translocase deficiency patients compared with other FAODs and needs further investigation.
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Affiliation(s)
- Marie K Norris
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah, USA.,Department of Nutrition, Biochemical Genetics, Seattle Children's Hospital, Seattle, Washington, USA
| | - Anna I Scott
- Department of Laboratories, Biochemical Genetics, Seattle Children's Hospital, Seattle, Washington, USA
| | - Sarah Sullivan
- Department of Nutrition, Biochemical Genetics, Seattle Children's Hospital, Seattle, Washington, USA
| | - Irene J Chang
- Department of Pediatrics, Biochemical Genetics, University of Washington, Seattle Children's Hospital, Seattle, Washington, USA
| | - Christina Lam
- Department of Pediatrics, Biochemical Genetics, University of Washington, Seattle Children's Hospital, Seattle, Washington, USA
| | - Angela Sun
- Department of Pediatrics, Biochemical Genetics, University of Washington, Seattle Children's Hospital, Seattle, Washington, USA
| | - Sihoun Hahn
- Department of Pediatrics, Biochemical Genetics, University of Washington, Seattle Children's Hospital, Seattle, Washington, USA
| | - Jenny M Thies
- Department of Pediatrics, Biochemical Genetics, University of Washington, Seattle Children's Hospital, Seattle, Washington, USA
| | - Melissa Gunnarson
- Department of Nutrition, Biochemical Genetics, Seattle Children's Hospital, Seattle, Washington, USA
| | - Kelly N McKean
- Department of Nutrition, Biochemical Genetics, Seattle Children's Hospital, Seattle, Washington, USA
| | - J Lawrence Merritt
- Department of Pediatrics, Biochemical Genetics, University of Washington, Seattle Children's Hospital, Seattle, Washington, USA
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8
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Miller DE, Ferreira CR, Scott AI, Chang IJ. Pharmacokinetics of oral l-serine supplementation in a single patient. Mol Genet Metab Rep 2020; 24:100607. [PMID: 32489882 PMCID: PMC7256326 DOI: 10.1016/j.ymgmr.2020.100607] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 05/07/2020] [Indexed: 11/20/2022] Open
Abstract
Serine, a non-essential amino acid, has attracted clinical attention because of potential benefit in certain metabolic and neurological disorders. Despite the therapeutic potential, little is known about the pharmacokinetics of l-serine metabolism in humans. Here we present pharmacokinetic data at the time of treatment initiation as well as plasma serine levels during dose escalation from a single individual taking oral l-serine as part of a treatment regimen. Our results show that plasma serine levels rise and fall rapidly after oral l-serine intake, suggesting that the optimal dosing for oral l-serine supplementation is at least three times per day.
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Affiliation(s)
- Danny E. Miller
- Department of Medicine, Division of Medical Genetics, University of Washington, Seattle, Washington, USA
- Department of Pediatrics, Division of Genetic Medicine, University of Washington, Seattle, Washinghton and Seattle Children's Hospital, Seattle, Washington, USA
| | - Carlos R. Ferreira
- National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - Anna I. Scott
- Department of Laboratories, Seattle Children's Hospital, Seattle, Washington, USA
- Department of Laboratory Medicine, University of Washington, Seattle, Washington, USA
| | - Irene J. Chang
- Department of Pediatrics, Division of Genetic Medicine, University of Washington, Seattle, Washinghton and Seattle Children's Hospital, Seattle, Washington, USA
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9
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Course MM, Scott AI, Schoor C, Hsieh CH, Papakyrikos AM, Winter D, Cowan TM, Wang X. Phosphorylation of MCAD selectively rescues PINK1 deficiencies in behavior and metabolism. Mol Biol Cell 2018; 29:1219-1227. [PMID: 29563254 PMCID: PMC5935071 DOI: 10.1091/mbc.e18-03-0155] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
PTEN-induced putative kinase 1 (PINK1) is a mitochondria-targeted kinase whose mutations are a cause of Parkinson’s disease. We set out to better understand PINK1’s effects on mitochondrial proteins in vivo. Using an unbiased phosphoproteomic screen in Drosophila, we found that PINK1 mediates the phosphorylation of MCAD, a mitochondrial matrix protein critical to fatty acid metabolism. By mimicking phosphorylation of this protein in a PINK1 null background, we restored PINK1 null’s climbing, flight, thorax, and wing deficiencies. Owing to MCAD’s role in fatty acid metabolism, we examined the metabolic profile of PINK1 null flies, where we uncovered significant disruptions in both acylcarnitines and amino acids. Some of these disruptions were rescued by phosphorylation of MCAD, consistent with MCAD’s rescue of PINK1 null’s organismal phenotypes. Our work validates and extends the current knowledge of PINK1, identifies a novel function of MCAD, and illuminates the need for and effectiveness of metabolic profiling in models of neurodegenerative disease.
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Affiliation(s)
- Meredith M Course
- Department of Neurosurgery, Stanford University, Stanford, CA 94305.,Neurosciences Graduate Program, Stanford University, Stanford, CA 94305
| | - Anna I Scott
- Department of Pathology, Stanford University, Stanford, CA 94305
| | - Carmen Schoor
- Institute for Biochemistry and Molecular Biology, University of Bonn, 53115 Bonn, Germany
| | - Chung-Han Hsieh
- Department of Neurosurgery, Stanford University, Stanford, CA 94305
| | - Amanda M Papakyrikos
- Department of Neurosurgery, Stanford University, Stanford, CA 94305.,Developmental Biology Graduate Program, Stanford University, Stanford, CA 94305
| | - Dominic Winter
- Institute for Biochemistry and Molecular Biology, University of Bonn, 53115 Bonn, Germany
| | - Tina M Cowan
- Department of Pathology, Stanford University, Stanford, CA 94305
| | - Xinnan Wang
- Department of Neurosurgery, Stanford University, Stanford, CA 94305
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10
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Strovel ET, Cowan TM, Scott AI, Wolf B. Erratum: Laboratory diagnosis of biotinidase deficiency, 2017 update: a technical standard and guideline of the American College of Medical Genetics and Genomics. Genet Med 2018; 20:282. [DOI: 10.1038/gim.2017.201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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11
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Gwinn DM, Lee AG, Briones-Martin-Del-Campo M, Conn CS, Simpson DR, Scott AI, Le A, Cowan TM, Ruggero D, Sweet-Cordero EA. Oncogenic KRAS Regulates Amino Acid Homeostasis and Asparagine Biosynthesis via ATF4 and Alters Sensitivity to L-Asparaginase. Cancer Cell 2018; 33:91-107.e6. [PMID: 29316436 PMCID: PMC5761662 DOI: 10.1016/j.ccell.2017.12.003] [Citation(s) in RCA: 140] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Revised: 05/25/2017] [Accepted: 12/07/2017] [Indexed: 12/19/2022]
Abstract
KRAS is a regulator of the nutrient stress response in non-small-cell lung cancer (NSCLC). Induction of the ATF4 pathway during nutrient depletion requires AKT and NRF2 downstream of KRAS. The tumor suppressor KEAP1 strongly influences the outcome of activation of this pathway during nutrient stress; loss of KEAP1 in KRAS mutant cells leads to apoptosis. Through ATF4 regulation, KRAS alters amino acid uptake and asparagine biosynthesis. The ATF4 target asparagine synthetase (ASNS) contributes to apoptotic suppression, protein biosynthesis, and mTORC1 activation. Inhibition of AKT suppressed ASNS expression and, combined with depletion of extracellular asparagine, decreased tumor growth. Therefore, KRAS is important for the cellular response to nutrient stress, and ASNS represents a promising therapeutic target in KRAS mutant NSCLC.
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Affiliation(s)
- Dana M Gwinn
- Division of Hematology and Oncology, Department of Pediatrics, Stanford University School of Medicine, Stanford, CA 94305, USA; Division of Hematology and Oncology, Department of Pediatrics, University of California San Francisco, San Francisco, CA 94158, USA
| | - Alex G Lee
- Division of Hematology and Oncology, Department of Pediatrics, Stanford University School of Medicine, Stanford, CA 94305, USA; Division of Hematology and Oncology, Department of Pediatrics, University of California San Francisco, San Francisco, CA 94158, USA
| | - Marcela Briones-Martin-Del-Campo
- Division of Hematology and Oncology, Department of Pediatrics, University of California San Francisco, San Francisco, CA 94158, USA
| | - Crystal S Conn
- School of Medicine and Department of Urology, Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94158, USA
| | - David R Simpson
- Division of Hematology and Oncology, Department of Pediatrics, Stanford University School of Medicine, Stanford, CA 94305, USA; Division of Hematology and Oncology, Department of Pediatrics, University of California San Francisco, San Francisco, CA 94158, USA
| | - Anna I Scott
- Stanford University, Department of Pathology, Stanford, CA 94305, USA
| | - Anthony Le
- Stanford University, Department of Pathology, Stanford, CA 94305, USA
| | - Tina M Cowan
- Stanford University, Department of Pathology, Stanford, CA 94305, USA
| | - Davide Ruggero
- School of Medicine and Department of Urology, Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94158, USA
| | - E Alejandro Sweet-Cordero
- Division of Hematology and Oncology, Department of Pediatrics, Stanford University School of Medicine, Stanford, CA 94305, USA; Division of Hematology and Oncology, Department of Pediatrics, University of California San Francisco, San Francisco, CA 94158, USA.
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12
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Scott AI, Cusmano-Ozog K, Enns GM, Cowan TM. Correction of hyperleucinemia in MSUD patients on leucine-free dietary therapy. Mol Genet Metab 2017; 122:156-159. [PMID: 29032949 DOI: 10.1016/j.ymgme.2017.09.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Revised: 09/30/2017] [Accepted: 09/30/2017] [Indexed: 12/31/2022]
Abstract
PURPOSE Maple Syrup Urine Disease (MSUD) is a rare disorder of branched-chain amino acid catabolism associated with encephalopathy from accumulation of leucine. Leucine is closely monitored during normal growth and particularly during acute illness. As most hospitals do not have access to rapid plasma amino acid quantification, the initial management is often empirical. A model describing the reduction of plasma leucine in hyperleucinemic patients on leucine-free formula would help to guide management and optimize testing frequency. METHODS We retrospectively reviewed charts from 15 MSUD patients comprising 29 episodes of hyperleucinemia that were managed with leucine-free formula. Episodes were categorized by clinical presentation. RESULTS Upon leucine restriction, plasma leucine concentrations fell exponentially at a rate proportional to approximately 50% of the starting value over each 24-hour period. Recovery appears to be sensitive to clinical status and triggering event of the hyperleucinemic episode. Patients with upper respiratory infections generally recovered slowly, while cases of dietary non-adherence resolved more quickly. CONCLUSION This general model may help anticipate leucine levels during clinical management of MSUD patients when using nutritional support and leucine-free formula. The response of individual patients may vary depending on clinical status and triggering factors.
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Affiliation(s)
- Anna I Scott
- Department of Pathology, Stanford University School of Medicine, Stanford, CA, United States
| | - Kristina Cusmano-Ozog
- Biochemical Genetics and Metabolism Laboratory, Children's National Medical Center, Washington, DC, United States
| | - Gregory M Enns
- Department of Pediatrics, Stanford University School of Medicine, Stanford, CA, United States
| | - Tina M Cowan
- Department of Pathology, Stanford University School of Medicine, Stanford, CA, United States.
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13
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Gomez-Ospina N, Scott AI, Oh GJ, Potter D, Goel VV, Destino L, Baugh N, Enns GM, Niemi AK, Cowan TM. Expanding the phenotype of hawkinsinuria: new insights from response to N-acetyl-L-cysteine. J Inherit Metab Dis 2016; 39:821-829. [PMID: 27488560 DOI: 10.1007/s10545-016-9963-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Revised: 06/19/2016] [Accepted: 07/04/2016] [Indexed: 10/21/2022]
Abstract
Hawkinsinuria is a rare disorder of tyrosine metabolism that can manifest with metabolic acidosis and growth arrest around the time of weaning off breast milk, typically followed by spontaneous resolution of symptoms around 1 year of age. The urinary metabolites hawkinsin, quinolacetic acid, and pyroglutamic acid can aid in identifying this condition, although their relationship to the clinical manifestations is not known. Herein we describe clinical and laboratory findings in two fraternal twins with hawkinsinuria who presented with failure to thrive and metabolic acidosis. Close clinical follow-up and laboratory testing revealed previously unrecognized hypoglycemia, hypophosphatemia, combined hyperlipidemia, and anemia, along with the characteristic urinary metabolites, including massive pyroglutamic aciduria. Treatment with N-acetyl-L-cysteine (NAC) restored normal growth and normalized or improved most biochemical parameters. The dramatic response to NAC therapy supports the idea that glutathione depletion plays a key role in the pathogenesis of hawkinsinuria.
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Affiliation(s)
- Natalia Gomez-Ospina
- Department of Pediatrics, Stanford University School of Medicine, 300 Pasteur Drive, H 315, Stanford, CA, 94305-5208, USA.
| | - Anna I Scott
- Department of Pathology, Stanford University School of Medicine, Stanford, CA, USA
| | - Gia J Oh
- Department of Pediatrics, Stanford University School of Medicine, 300 Pasteur Drive, H 315, Stanford, CA, 94305-5208, USA
| | - Donald Potter
- Department of Pediatrics, Stanford University School of Medicine, 300 Pasteur Drive, H 315, Stanford, CA, 94305-5208, USA
| | - Veena V Goel
- Department of Pediatrics, Stanford University School of Medicine, 300 Pasteur Drive, H 315, Stanford, CA, 94305-5208, USA
| | - Lauren Destino
- Department of Pediatrics, Stanford University School of Medicine, 300 Pasteur Drive, H 315, Stanford, CA, 94305-5208, USA
| | - Nancy Baugh
- Department of Pediatrics, Stanford University School of Medicine, 300 Pasteur Drive, H 315, Stanford, CA, 94305-5208, USA
| | - Gregory M Enns
- Department of Pediatrics, Stanford University School of Medicine, 300 Pasteur Drive, H 315, Stanford, CA, 94305-5208, USA
| | - Anna-Kaisa Niemi
- Department of Pediatrics, Stanford University School of Medicine, 300 Pasteur Drive, H 315, Stanford, CA, 94305-5208, USA
| | - Tina M Cowan
- Department of Pediatrics, Stanford University School of Medicine, 300 Pasteur Drive, H 315, Stanford, CA, 94305-5208, USA
- Department of Pathology, Stanford University School of Medicine, Stanford, CA, USA
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14
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Abstract
The acquisition and sequencing of the genes encoding the enzymes for vitamin B12 biosynthesis in Salmonella typhimurium and Pseudomonas denitrificans has dramatically altered the direction of research on the pathway from uroporphyrinogen III to the corrinoids. Through a combination of molecular biology, organic chemistry and NMR spectroscopy, logical progression along the sequence is being made. Recent work from our laboratory is focused on the discovery and specificities of the methyltransferases connecting uroporphyrinogen III with cobyrinic acid, the temporal resolution of cobalt insertion and a comparison of the anaerobic pathway in S. typhimurium and the aerobic pathway in Ps. denitrificans. The implication of two parallel routes to corrins in these bacteria is discussed.
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Affiliation(s)
- A I Scott
- Department of Chemistry, Texas A&M University, College Station 77843-3255
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15
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Roessner CA, Ponnamperuma K, Scott AI. Mutagenesis identifies a conserved tyrosine residue important for the activity of uroporphyrinogen III synthase from Anacystis nidulans. FEBS Lett 2002; 525:25-8. [PMID: 12163155 DOI: 10.1016/s0014-5793(02)03056-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Uroporphyrinogen III synthase from the cyanobacterium Anacystis nidulans was overproduced in Escherichia coli and analyzed by site specific mutagenesis. Of the nine conserved amino acids altered, only a single tyrosine mutant (Y166F) showed any significant decrease in activity suggesting this residue is critical for proper substrate binding and/or catalysis.
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Affiliation(s)
- Charles A Roessner
- Center for Biological NMR, Department of Chemsitry, P.O. Box 30012, Texas A&M University, College Station, TX 77842-3012, USA.
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16
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Abstract
The biosynthesis of vitamin B(12) is summarized, emphasizing the differences observed between the aerobic and anaerobic pathways. The biosynthetic route to adenosylcobalamin from its five-carbon precursor, 5-aminolaevulinic acid, can be divided into three sections: (1) the biosynthesis of uroporphyrinogen III from 5-aminolaevulinic acid, which is common to both pathways; (2) the conversion of uroporphyrinogen III into the ring-contracted, deacylated intermediate precorrin 6 or cobalt-precorrin 6, which includes the primary differences between the two pathways; and (3) the transformation of this intermediate to form adenosylcobalamin.
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Affiliation(s)
- A I Scott
- Department of Chemistry, Texas A&M University, College Station, TX 77843-3255, USA.
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17
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Abstract
The chronology of the discoveries along the pathway of vitamin B12 biosynthesis is reviewed from a personal perspective, including discussion of the most recent finding that two pathways to B12 exist--one aerobic and one anaerobic--which differ mainly in the ring contraction mechanisms which convert porphyrin to corrin.
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Affiliation(s)
- A I Scott
- Center for Biological NMR, Chemistry Department, Texas A&M University, College Station 77843-3255, USA.
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18
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Abstract
The multiple actions of sterol carrier protein-2 (SCP-2) in intracellular lipid circulation and metabolism originate from its gene and protein structure. The SCP-x/pro-SCP-2 gene is a fusion gene with separate initiation sites coding for 15-kDa pro-SCP-2 (no enzyme activity) and 58-kDa SCP-x (a 3-ketoacyl CoA thiolase). Both proteins share identical cDNA and amino acid sequences for 13-kDa SCP-2 at their C-termini. Cellular 13-kDa SCP-2 derives from complete, posttranslational cleavage of the 15-kDa pro-SCP-2 and from partial posttranslational cleavage of 58-kDa SCP-x. Putative physiological functions of SCP-2 have been proposed on the basis of enhancement of intermembrane lipid transfer (e.g., cholesterol, phospholipid) and activation of enzymes involved in fatty acyl CoA transacylation (cholesterol esters, phosphatidic acid) in vitro, in transfected cells, and in genetically manipulated animals. At least four important SCP-2 structural domains have been identified and related to specific functions. First, the 46-kDa N-terminal presequence present in 58-kDa SCP-x is a 3-ketoacyl-CoA thiolase specific for branched-chain acyl CoAs. Second, the N-terminal 20 amino acid presequence in 15-kDa pro-SCP-2 dramatically modulates the secondary and tertiary structure of SCP-2 as well as potentiating its intracellular targeting coded by the C-terminal peroxisomal targeting sequence. Third, the N-terminal 32 amino acids form an amphipathic a-helical region, one face of which represents a membrane-binding domain. Positively charged amino acid residues in one face of the amphipathic helices allow SCP-2 to bind to membrane surfaces containing anionic phospholipids. Fourth, the hydrophobic faces of the N-terminal amphipathic a helices along with beta strands 4, 5, and helix D form a ligand-binding cavity able to accommodate multiple types of lipids (e. g., fatty acids, fatty acyl CoAs, cholesterol, phospholipids, isoprenoids). Two-dimensional 1H-15N heteronuclear single quantum coherence spectra of both apo-SCP-2 and of the 1:1 oleate-SCP-2 complex, obtained at pH 6.7, demonstrated the homogenous formation of holo-SCP-2. While comparison of the apo- and holoprotein amide fingerprints revealed about 60% of the resonances remaining essentially unchanged, 12 assigned amide residues underwent significant chemical-shift changes upon oleic acid binding. These residues were localized in three regions: the juncture of helices A and B, the mid-section of the beta sheet, and the interface formed by the region of beta strands 4, 5, and helix D. Circular dichroism also showed that these chemical-shift changes, upon oleic acid binding, did not alter the secondary structure of SCP-2. The nuclear magnetic resonance chemical shift difference data, along with mapping of the nearby hydrophobic residues, showed the oleic acid-binding site to be comprised of a pocket created by the face of the beta sheet, helices A and B on one end, and residues associated with beta strands 4, 5, and helix D at the other end of the binding cavity. Furthermore, the hydrophobic nature of the previously ill-defined C-terminus suggested that these 20 amino acids may form a 'hydrophobic cap' which closes around the oleic acid upon binding. Thus, understanding the structural domains of the SCP-x/pro-SCP-2 gene and its respective posttranslationally processed proteins has provided new insights into their functions in intracellular targeting and metabolism of lipids.
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Affiliation(s)
- N J Stolowich
- Department of Chemistry, University of Louisville, Kentucky 40292, USA
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19
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Scott AI, Cull RE. Unilateral, prolonged, nonconvulsive cerebral seizure activity in ECT. J ECT 2001; 17:292-3. [PMID: 11731733 DOI: 10.1097/00124509-200112000-00011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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20
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Huang Q, Roessner CA, Croteau R, Scott AI. Engineering Escherichia coli for the synthesis of taxadiene, a key intermediate in the biosynthesis of taxol. Bioorg Med Chem 2001; 9:2237-42. [PMID: 11553461 DOI: 10.1016/s0968-0896(01)00072-4] [Citation(s) in RCA: 139] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Taxadiene, the key intermediate of paclitaxel (Taxol) biosynthesis, has been prepared enzymatically from isopentenyl diphosphate in cell-free extracts of Escherichia coli by overexpressing genes encoding isopentenyl diphosphate isomerase, geranylgeranyl diphosphate synthase and taxadiene synthase. In addition, by the expression of three genes encoding four enzymes on the terpene biosynthetic pathway in a single strain of E. coli, taxadiene can be conveniently synthesized in vivo, at the unoptimized yield of 1.3mg per liter of cell culture. The success of both in vitro and in vivo synthesis of taxadiene bodes well for the future production of taxoids by non-paclitaxel producing organisms through pathway engineering.
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Affiliation(s)
- Q Huang
- Center for Biological NMR, Department of Chemistry, PO Box 30012, Texas A & M University, College Station, TX 77842-3012, USA
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21
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Abstract
BACKGROUND The crystal structure of precorrin-8x methyl mutase (CobH), an enzyme of the aerobic pathway to vitamin B12, provides evidence that the mechanism for methyl migration can plausibly be regarded as an allowed [1,5]-sigmatropic shift of a methyl group from C-11 to C-12 at the C ring of precorrin-8x to afford hydrogenobyrinic acid. RESULTS The dimeric structure of CobH creates a set of shared active sites that readily discriminate between different tautomers of precorrin-8x and select a discrete tautomer for sigmatropic rearrangement. The active site contains a strictly conserved histidine residue close to the site of methyl migration in ring C of the substrate. CONCLUSION Analysis of the structure with bound product suggests that the [1,5]-sigmatropic shift proceeds by protonation of the ring C nitrogen, leading to subsequent methyl migration.
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Affiliation(s)
- L W Shipman
- Department of Chemistry, Texas A&M University, College Station, TX 77843, USA.
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22
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Abstract
The manner in which vitamin B12 is synthesized is detailed with emphasis on the different mechanisms for ring contraction encountered in aerobic and anaerobic organisms. The aerobic process utilizes two enzymes and is dependent on molecular oxygen, in stark contrast to the anaerobic mechanism which is controlled by cobalt and requires only one enzyme.
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Affiliation(s)
- C A Roessner
- Center for Biological NMR, Department of Chemistry, Texas A&M University, College Station, Texas 77843, USA
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23
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Abstract
An improved route was developed for the preparation of the dinucleotide hybrid 5'-O-phosphoryl-2'-deoxycytidylyl-(3'--> 5')adenosine (pdCpA) 7. This simple and concise synthesis involves the successive coupling of 2-cyanoethyl N, N, N', N'-tetra- isopropylphosphorodiamidite with 4-N-benzoyl-5'-O-(4, 4'-dimethoxytrityl)-2'-deoxy-cytidine 1 and 6-N,6-N,2'-O,3'-O-tetrabenzoyladenosine 2 as the key step. Some dinucleotide derivatives bearing different protecting groups were also synthesized and the selective deprotection conditions were studied in detail. The utility and efficiency of this approach has been further demonstrated by its application to the synthesis of total DNA dinucleotide pdCpdA 17 and total RNA dinucleotide 21.
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Affiliation(s)
- X F Zhu
- Center for Biological NMR, Department of Chemistry, Texas A&M University, College Station 77842-3012, USA
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24
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Abstract
Evidence-based medicine is fine in principle, but needs to demonstrate tangible benefits to clinicians and their patients in practice. The main obstacles to its implementation are: (a) identifying information needs; (b) delivering reliable and clinically useful information to the ward/clinic; and (c) ensuring the information is regularly updated. How can this be achieved in psychiatry?
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25
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Abstract
The dosage of methohexitone (methohexital) administered by anesthetic staff was surveyed in a consecutive series of 52 patients referred for electroconvulsive therapy (ECT) in routine clinical practice in Edinburgh. Patients were weighed before the first treatment, and the ratio of administered dose to weight in kilograms calculated. Anesthesia was administered by three consultant staff and six nonconsultant staff. In only one patient (2%) was the administered dose within the range recommended by the Royal College of Psychiatrists (0.75-0.9 mg/kg), and in only four patients (8%) were the doses within the range recommended by the American Psychiatric Association (0.75-1.0 mg/kg). In all other patients the dose exceeded these recommended ranges; the average dose was 1.5 (+/- 0.3) mg/kg. The possible implications of these findings are discussed.
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Affiliation(s)
- A Cook
- Monklands District General Hospital, Airdrie, Scotland, United Kingdom
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26
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Scott AI, Clarke BE, Healy H, D Emden M, Bell SC. Microvascular complications in cystic fibrosis-related diabetes mellitus: a case report. JOP 2000; 1:208-10. [PMID: 11856863] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
CONTEXT, The prevalence of cystic fibrosis-related diabetes mellitus is increasing and is associated with increased survival from cystic fibrosis. CASE REPORT, This study describes a case of the premature onset of disabling and widespread microvascular complications resulting from cystic fibrosis-related diabetes mellitus. Previously asymptomatic retinopathy was diagnosed on recognition of diabetic nephropathy. CONCLUSIONS, The treatment of pulmonary exacerbations has become more complex due to the nephrotoxic potential of intravenous aminoglycoside drugs which are frequently used to control chronic Pseudomonas infection in cystic fibrosis.
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Affiliation(s)
- A I Scott
- Adult Cystic Fibrosis Unit, University of Queensland, The Prince Charles Hospital. Chermside, Queensland, Australia
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28
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Abstract
Seizure threshold was measured by empirical titration in 28 patients referred for bilateral electroconvulsive therapy to treat depressive illness at the outset of treatment and after another six treatments. No patient was given antiepileptic drug treatment, and anesthetic technique and concomitant psychotropic drug treatment were fixed. The average (+/- SD) initial seizure threshold measured by set charge was 79.5 mC (+/- 33.4 mC), and this increased to 95.5 mC (+/- 37.9 mC). The average percentage increase was 22.8% (95% confidence interval, 13.7% to 31.8%). The seizure threshold measured by set charge did not change in 15 patients (54%), and there was no significant relation between change in seizure threshold and patient sex, change in seizure duration measured by cuff technique, or global clinical improvement during the course of treatment.
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Affiliation(s)
- A I Scott
- Andrew Duncan Clinic, Royal Edinburgh Hospital, Edinburgh, Scotland, United Kingdom
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29
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Abstract
BACKGROUND Critics of electroconvulsive therapy (ECT) have expressed concern about variations in ECT use among consultant teams within the same hospital. The aim was to establish whether or not there was a significant variation in rates of ECT use among consultant teams in the same hospital when in-patient workload was taken into account. METHODS A computerised database was used to calculate annual and aggregate rates of ECT use by consultant team, expressed as the number of individual in-patients treated per 100 in-patients discharged between 1993 and 1996. RESULTS The variation in aggregate rates of ECT use varied approximately 18-fold among the 11 general adult psychiatric teams (P<0.001), and twofold among the three sector old-age psychiatric teams (P<0.05). CONCLUSIONS Substantial variation in the rates of ECT use was confirmed, but only among general adult psychiatric teams. LIMITATIONS The extent to which findings from one teaching hospital can be generalised was unknown. Possible explanations of the variations were not assessed.
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Affiliation(s)
- T Glen
- Andrew Duncan Clinic, Royal Edinburgh Hospital, Edinburgh, UK
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30
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Lawrie SM, Scott AI, Sharpe MC. Evidence-based psychiatry--do psychiatrists want it and can they do it? Health Bull (Edinb) 2000; 58:25-33. [PMID: 12813849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 03/03/2023]
Abstract
OBJECTIVE To examine (a) psychiatrists' attitudes to evidence-based psychiatry, (b) whether psychiatrists have identifiable clinical information needs, (c) if such information is practically obtainable, and (d) how psychiatrists respond to the information obtained. DESIGN We surveyed senior psychiatrists to enquire about their attitudes and to request up to three clinical questions they would like answered. We attempted to find evidence to answer the five most frequently asked questions using recommended strategies and timed how long it took us. We fed our answers back to those who had asked one of these questions and asked if they found the answers useful. SETTING Specialist registrars, senior registrars and consultants in south-east Scotland. RESULTS Ninety three (76%) of those surveyed returned usable questionnaires. Respondents thought that only 40% of their practice is evidence-based. They reported that 'insufficient time' was the biggest barrier to implementing evidence-based psychiatry. The most frequently asked questions concerned the treatment of major psychiatric disorders. It took us--three experienced researchers, trained in critical appraisal, with excellent local facilities--between 15-60 minutes to answer each question. Most of those who had asked the questions (15/22) thought they would not have been able to answer them and stated that such a 'question answering service' as piloted here would be valuable. CONCLUSIONS An evidence-based psychiatry appears to be desirable and possible, but impractical for the individual clinician. There is a need for short accessible evidence-based summaries of optimal treatment in psychiatry.
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Affiliation(s)
- S M Lawrie
- Edinburgh Healthcare NHS Trust, Edinburgh
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Stolowich N, Frolov A, Petrescu AD, Scott AI, Billheimer JT, Schroeder F. Holo-sterol carrier protein-2. (13)C NMR investigation of cholesterol and fatty acid binding sites. J Biol Chem 1999; 274:35425-33. [PMID: 10585412 DOI: 10.1074/jbc.274.50.35425] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Although sterol carrier protein-2 (SCP-2) stimulates sterol transfer in vitro, almost nothing is known regarding the identity of the putative cholesterol binding site. Furthermore, the interrelationship(s) between this SCP-2 ligand binding site and the recently reported SCP-2 long chain fatty acid (LCFA) and long chain fatty acyl-CoA (LCFA-CoA) binding site(s) remains to be established. In the present work, two SCP-2 ligand binding sites were identified. First, both [4-(13)C]cholesterol and 22-(N-(7-nitrobenz-2-oxa-1, 3-diazol-4-yl)amino)-23,24-bisnor-5-cholen-3beta-ol (NBD-cholesterol) binding assays were consistent with a single cholesterol binding site in SCP-2. This ligand binding site had high affinity for NBD-cholesterol, K(d) = 4.15 +/- 0.71 nM. (13)C NMR-labeled ligand competition studies demonstrated that the SCP-2 high affinity cholesterol binding site also bound LCFA or LCFA-CoA. However, only the LCFA-CoA was able to effectively displace the SCP-2-bound [4-(13)C]cholesterol. Thus, the ligand affinities at this SCP-2 binding site were in the relative order cholesterol = LCFA-CoA > LCFA. Second, (13)C NMR studies demonstrated the presence of another ligand binding site on SCP-2 that bound either LCFA or LCFA-CoA but not cholesterol. Photon correlation spectroscopy was consistent with SCP-2 being monomeric in both liganded and unliganded states. In summary, both (13)C NMR and fluorescence techniques demonstrated for the first time that SCP-2 had a single high affinity binding site that bound cholesterol, LCFA, or LCFA-CoA. Furthermore, results with (13)C NMR supported the presence of a second SCP-2 ligand binding site that bound either LCFA or LCFA-CoA but not cholesterol. These data contribute to our understanding of a role for SCP-2 in both cellular cholesterol and LCFA metabolism.
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Affiliation(s)
- N Stolowich
- Department of Chemistry, Texas A & M University, College Station, Texas 77843-4466, USA
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Huang KX, Scott AI, Bennett GN. Overexpression, purification, and characterization of the thermostable mevalonate kinase from Methanococcus jannaschii. Protein Expr Purif 1999; 17:33-40. [PMID: 10497066 DOI: 10.1006/prep.1999.1106] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We report here the first overexpression and characterization of a thermostable mevalonate kinase from an archae, Methanococcus jannaschii, a strict anaerobe, which produces methane and grows at pressure of 200 atm and an optimum temperature near 85 degrees C. PCR-derived DNA fragments containing the structural gene for mevalonate kinase were cloned into an expression vector, pET28a, to form pETMVK. The mevalonate kinase was overexpressed from Escherichia coli pETMVK/BL21(DE3) (15-20% of total soluble protein) when induced with isopropyl beta-d-thiogalactopyranoside. The protein was purified by heat treatment (to denature E. coli proteins), followed by metal-affinity chromatography on Talon metal-affinity resin column. The purified protein had a dimeric structure composed of identical subunits, and the M(r) of the enzyme determined by gel chromatography was 68K. Based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the subunit M(r) was 36, 000. The pI for mevalonate kinase was 7.8. The Michaelis constant (K(m)) for (RS)-mevalonate was 68.5 microM and was 92 microM for ATP. The V(max) was 387 units mg(-1). The optimal temperature for mevalonate kinase activity was 70-75 degrees C.
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Affiliation(s)
- K X Huang
- Department of Biochemistry and Cell Biology, Rice University, 6100 Main Street, Houston, Texas 77005-1892, USA
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Abstract
The construction of a new recombinant strain of Escherichia coli in which two vitamin B12 biosynthetic genes, cobA and cobI, from Pseudomonas denitrificans are simultaneously overexpressed has resulted in the in vivo synthesis and accumulation of Factor III, an isobacteriochlorin not normally synthesized in E. coli. A lysate of the new strain can take the place of two lysates normally required to provide uroporphyrinogen III methyltransferase (cobA) and precorrin-2 methyltransferase (cobI) in an anaerobic five-enzyme synthesis of the early B12 intermediate, precorrin-3 (the reduced form of Factor III) from delta-aminolevulinic acid.
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Affiliation(s)
- C A Roessner
- Department of Chemistry, Texas A&M University, College Station 77842-3012, USA
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Abstract
BACKGROUND The number of ECT treatments given each year is a topic of interest for psychiatrists, users and politicians, but there are major methodological problems in reported studies of rates of ECT use in the British Isles. The aim was to establish whether or not the use of ECT had fallen between 1992 and 1997. METHOD A computerised database of ECT treatments in Edinburgh and relevant population data were used to calculate annual indices of ECT usage. These indices were calculated separately for the population aged 18-64 years and those 65 years or older. RESULTS In the general adult population, the rate of ECT use fell progressively and significantly (p < 0.01) from 2.90 to 1.37 treatments per 1000 population. This fall was commensurate with the falls in other indices of ECT use. Among the elderly population, the rate of ECT use was three times that in the general adult population. There was no significant change, although the number of courses of treatment fell by 40% (p = 0.06). CONCLUSIONS There continues to be a progressive fall in the use of ECT in general adult psychiatry. ECT is used substantially more often in the elderly. Reports of ECT use ought to include numbers of both treatments and patients treated. LIMITATIONS There was no investigation of the possible causes of the fall in ECT use. The extent to which these findings can be generalised to the rest of the British Isles will require further study.
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Affiliation(s)
- T Glen
- Andrew Duncan Clinic, Royal Edinburgh Hospital, UK
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Scott AI, Dykes S. Initial seizure threshold in the clinical practice of bilateral electroconvulsive therapy in Edinburgh, Scotland. J ECT 1999; 15:118-24. [PMID: 10378150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
Initial seizure threshold was measured by empirical titration in 137 patients referred for bilateral electroconvulsive therapy (ECT) for the treatment of depressive illness. Treatment was given by an Ectron Series 5A ECT machine. The median and modal thresholds were 75 mC and the range was 50-200 mC. The only statistically significant relationship among initial threshold and age or gender was the correlation of age with threshold in men (rho = 0.46, p < 0.01). All patients (n = 22) younger than 30 years had an initial threshold < 100 mC, but age and gender did not predict threshold accurately for older men or women.
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Affiliation(s)
- A I Scott
- Andrew Duncan Clinic, Royal Edinburgh Hospital, Scotland
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Abstract
The chemoenzymatic synthesis and structural characterization by 13C NMR of a tetramethyl cobalt-corphinoid produced by methylation of cobalt-precorrin-3 using CbiF are described.
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Affiliation(s)
- P J Santander
- Department of Chemistry, Texas A&M University, College Station 77842-3012, USA
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Abstract
The preferred conformations of the active diuretic insect kinin pentapeptide analogue Phe-Phe-Aib-Trp-Gly-NH2 were studied using nmr spectroscopy and molecular modeling. Structure sets consistent with rotating frame nuclear Overhauser effect spectroscopy distance constraints obtained by restrained simulated annealing in vacuo indicate a predominant population of a type II beta-turn involving the Phe1-Trp4 region. An equilibrium between this type II and a type I beta-turn formed by residues Phe2 and Gly5 was observed in a 5 ns restrained molecular dynamics simulation using the implicit generalized Born solvent accessible surface area (GB/SA) solvation model. When subjected to 500 ps dynamics with explicit water both beta-turn folds were conserved throughout the simulations. The results obtained with implicit and explicit solvation models are compared, and their consistency with the nmr observations is discussed. The behavior of the linear pentapeptide in this study is in agreement with an earlier report on the consensus conformation of the insect kinin active core derived from analysis of cyclic active analogues.
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Affiliation(s)
- G Moyna
- Department of Chemistry, Texas A&M University, College Station 77842-3012, USA
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Moyna G, Williams HJ, Nachman RJ, Scott AI. Detection of nascent polyproline II helices in solution by NMR in synthetic insect kinin neuropeptide mimics containing the X-Pro-Pro-X motif. J Pept Res 1999; 53:294-301. [PMID: 10231717 DOI: 10.1034/j.1399-3011.1999.00036.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The conformations of three synthetic peptide analogs containing the dPro-dPro-dXaa motif (dXaa = dThr, dGlu, dAsn) in aqueous solution were studied by a combination of NMR and molecular modeling simulations. The three compounds were identified from a random D-amino acid tripeptide library on the basis of their ability to either mimic or block the diuretic activity of neuropeptides of the insect kinin family. TOCSY and ROESY correlations, as well as abnormal secondary chemical shifts for protons on the D-proline residues were employed to obtain conformational ensembles consistent with the experimental NMR data for the three analogs using an in vacuo simulated annealing protocol. Similar secondary structures were found for the three molecules after refinement, in agreement with the similarities observed between their NMR spectra. Unrestrained molecular dynamics simulations with explicit water representation indicate that the structural motifs found in vacuo are stable in aqueous solution. The three analogs can be considered initiators of right-handed poly D-proline II helices, mirror images of the poly L-proline II left-handed helical motifs normally found in proline-rich proteins. The role of these secondary folds on binding of the analogs to the kinin receptors is discussed.
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Affiliation(s)
- G Moyna
- Department of Chemistry, Texas A & M University, College Station 77842-3012, USA
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Spencer P, Stolowich NJ, Sumner LW, Scott AI. Definition of the redox states of cobalt-precorrinoids: investigation of the substrate and redox specificity of CbiL from Salmonella typhimurium. Biochemistry 1998; 37:14917-27. [PMID: 9778368 DOI: 10.1021/bi981366f] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The enzyme CbiL from the facultative anaerobe Salmonella typhimurium exhibits a high degree of homology to CobI from the aerobe Pseudomonas denitrificans (29% identity; 51% conservation obtained by a Blastp search of the ncbi database). As CobI catalyzes the third methylation in the aerobic pathway to vitamin B12 it is proposed that CbiL catalyzes the analogous step in the anaerobic pathway. Potential metallo and metal-free substrates were characterized and their redox states defined by a combination of physicochemical techniques (MALDI-MS, NMR, UV/vis, IR, and EPR) and then used to investigate the function of CbiL. CbiL exhibited an absolute requirement for the presence of a metal ion (Co(II), Ni(II), or Zn(II)) within the tetrapyrrole substrate. CbiL had no preference for the redox state of its cobalt tetrapyrrole substrate, methylating both the reduced form, Co(II) 2, 7-dimethyl-dipyrrocorphin (Co(II)-precorrin-2), and the oxidized form, Co(III) 2,7-dimethyl-isobacterioclorin (Co(III)-factor-II). In contrast CbiL had a marked preference for the oxidized Ni(II) and Zn(II)-2,7-dimethyl-isobacteriochlorin (Ni(II) and Zn(II)-factor-II). Removal of the metal ion from a product of CbiL (Zn(II)-factor-III) allowed characterization by 13C NMR, identifying the tetrapyrrole as 2,7,20-trimethyl-isobacteriochlorin (factor-3), indicating that CbiL methylates at C20, the same site as that methylated by CobI. Competition experiments, utilizing isotopic labeling to distinguish otherwise identical mass substrates and products, revealed that oxidized Co(III) or Ni(II)-factor-II were equally good substrates, whereas Co(II)-precorrin-2 was much preferred over Ni(II)-precorrin-2. Excess Ni(II)-precorrin-2 did not decrease CbiL methylation of Co(II)-precorrin-2, implying that CbiL has a low affinity for Ni(II)-precorrin-2. These results are interpreted on the basis of tetrapyrrole ruffling occurring on the optimization of the metallo-N bond distances. The greater flexibility of the reduced precorrin-2 ring system allows greater deformation on accommodating the bound metal ion, the distortions imposed by bound Ni(II) or Zn(II) ions being larger than Co(II). The resulting distortions imposed on the precorrin ring could then decrease catalysis by causing a departure from the optimal substrate conformation required for CbiL. On oxidation of the Ni(II) or Zn(II)-precorrin-2, the increased stiffness of the ring could then constrain the metallo-factor-II conformation toward that of the usual substrate, allowing greater methylation by CbiL. In contrast to its counterpart CobI in the aerobic pathway of B12 biosynthesis, which methylates the metal-free precorrin-2, these studies show CbiL to be the first methylase unique to the anaerobic pathway, methylating a metallo-precorrin-2 substrate. Implications of CbiL specificity for the mechanism of the anaerobic B12 pathway are discussed.
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Affiliation(s)
- P Spencer
- Department of Chemistry, Texas A and M University, College Station 77843-3255, USA
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Nachman RJ, Moyna G, Williams HJ, Tobe SS, Scott AI. Synthesis, biological activity, and conformational studies of insect allatostatin neuropeptide analogues incorporating turn-promoting moieties. Bioorg Med Chem 1998; 6:1379-88. [PMID: 9784875 DOI: 10.1016/s0968-0896(98)00129-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
Allatostatins are 6-18 amino acid peptides synthezed by insects to control production of juvenile hormones, which in turn regulate functions including metamorphosis and egg production. Four insect allatostatin neuropeptide analogues incorporating turn-promoting pseudopeptide moieties in the region responsible for biological activity were prepared by solid phase peptide synthetic methods. Bioassay indicated that activities approached those of the natural neuropeptides, and molecular models based on NMR data showed similar conformations and the presence of a beta-turn in the active core region for the four analogues. Differences in activity are believed to be due to differences in bulk and relative position of atoms in the unnatural portion of the analogues, and their differing degrees of conformational freedom. The studies support the feasibility of development of neuropeptide-based insect control agents resistant to peptidase deactivation.
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Affiliation(s)
- R J Nachman
- Veterinary Entomology Research Unit, FAPRL, Agricultural Research Service, USDA, College Station, TX 77845-2122, USA
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Moyna G, Zauhar RJ, Williams HJ, Nachman RJ, Scott AI. Comparison of ring current methods for use in molecular modeling refinement of NMR derived three-dimensional structures. J Chem Inf Comput Sci 1998; 38:702-9. [PMID: 9691476 DOI: 10.1021/ci980402e] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
A comparison between three different methods commonly used to estimate ring current effects on chemical shifts is presented. Haigh-Mallion, Johnson-Bovey, and classical point-dipole approximations were used to estimate the ring current contribution to chemical shifts for protons in several proteins for which both detailed X-ray crystal structures and chemical shift assignments were available. For the classical point-dipole model, new proportionality constants were calculated by fitting to ring current estimations from both the quantum-mechanical Haigh-Mallion and semiclassical Johnson-Bovey methods and compared with the previously used point-dipole constant of Perkins and Dwek. Statistical analysis of the predictions obtained by all methods indicates that the point-dipole approximation parametrized against quantum-mechanical data is superior to the previously used classical model, comparable to Johnson-Bovey calculations, and slightly poorer than predictions from the Haigh-Mallion theory. The implementation of a pseudoenergy penalty term for use in structure refinement from chemical shift data based on the classical point-dipole model is described, and its usefulness in cases where other NMR information is limited is discussed with a specific example.
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Affiliation(s)
- G Moyna
- Department of Chemistry, Texas A&M University, College Station 77842-3012, USA
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Huang KX, Huang QL, Wildung MR, Croteau R, Scott AI. Overproduction, in Escherichia coli, of soluble taxadiene synthase, a key enzyme in the Taxol biosynthetic pathway. Protein Expr Purif 1998; 13:90-6. [PMID: 9631520 DOI: 10.1006/prep.1998.0870] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Taxadiene synthase catalyzes the conversion of the universal precursor of diterpenoids, geranylgeranyl diphosphate, to taxadiene, a key intermediate in Taxol (paclitaxel) biosynthesis. The gene encoding taxadiene synthase was cloned recently. Here we report a method for the heterologous overexpression of cDNA encoding taxadiene synthase in Escherichia coli using a thioredoxin fusion expression system, which increases the solubility of expressed protein. Taxadiene synthase cDNA was amplified by polymerase chain reaction and then subcloned into pET3d and pET32a(+) to form pET3dTX and pET32TX, respectively. The expressed taxadiene synthase from E. coli BL21(DE3)/pET3dTX was present completely as inclusion bodies. The transformant E. coli BL21(DE3)/pET32TX produced a thioredoxin fusion taxadiene synthase (15-20% of total soluble protein) when induced with isopropyl beta-D-thiogalactopyranoside at low temperature (20 degrees C). The recombinant enzyme was purified by a single step with a His-binding metal affinity column. The maximal production attained was 13 mg of purified, active fusion protein per 500 ml culture of E. coli BL21(DE3)/pET32TX. The purified recombinant taxadiene synthase fusion protein was similar to native protein in steady-state kinetic parameters and mobility on sodium sulfate-polyacrylamide gel electrophoresis. The protein purified from E. coli BL21(DE3)/pET3dTX had the expected N-terminal (AQLSFNA) sequence.
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Affiliation(s)
- K X Huang
- Chemistry Department, Texas A&M University, College Station 77843-3255, USA
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Abstract
Casbene synthase is a diterpene cyclase isolated from castor bean (Ricinus communis L), which catalyzes the cyclization of geranylgeranyl diphosphate to form the phytoalexin casbene. We here report the overexpression of casbene synthase in Escherichia coli in soluble form using a thioredoxin fusion system. The amplified DNA by PCR carried on pCS7 was inserted into the expression vector pET32b(+) to form pCAS.2. The resulting transformants of pCAS. 2/BL21(DE3) produced a thioredoxin casbene synthase fusion protein (20-30% of total soluble protein) when induced with isopropyl beta-d-thiogalactopyranoside at 20 degrees C. Recombinant casbene synthase was purified to homogeneity in a single step with a His-binding metal-affinity column. Casbene synthase has a conserved aspartate-rich region [amino acids 355-359 (DDTID)], one cysteine, and three histidines with several prenyl transferases and terpene cyclases. Seven mutants were constructed by site-directed mutagenesis. The importance of Asp 355 and Asp 356 for catalysis was established by an increase in Km as well as a reduction in kcat in the corresponding glutamate mutants. These results indicate that the first and the second aspartate are involved in catalysis, while the third aspartate and the conserved cysteine and histidine residues selected for mutagenesis appear not to be involved in catalysis.
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Affiliation(s)
- K Huang
- Chemistry Department, Texas A&M University, College Station, Texas 77843-3255, USA
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Abstract
Re-investigation of the aerial parts of Iva frutescens resulted in the isolation of three sesquiterpenes, two of which are new natural products, and their structures were established by spectral data.
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Affiliation(s)
- A A Ahmed
- Department of Chemistry, Faculty of Science, El-Minia University, Egypt
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Moyna G, Williams HJ, Scott AI, Ringel I, Gorodetsky R, Swindell CS. Conformational studies of paclitaxel analogs modified at the C-2' position in hydrophobic and hydrophilic solvent systems. J Med Chem 1997; 40:3305-11. [PMID: 9379451 DOI: 10.1021/jm970026+] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The conformations of two paclitaxel analogs modified at the C-2' position, 2'-deoxypaclitaxel and 2'-methoxypaclitaxel, were studied in hydrophobic and hydrophilic solvent systems by a combination of NMR spectroscopy, CD measurements, and molecular modeling. Both analogs have hydrophobic and hydrophilic conformations that resemble those of paclitaxel itself in the same media. Since the two have diminished biological activities in a number of bioactivity assays and the hydrogen-bonding capability of the 2'-hydroxyl group has been eliminated, we postulate that this group is involved in hydrogen bonding with tubulin and plays an important role in molecular recognition. The results of this study are in agreement with our earlier report on paclitaxel 2'-acetate, an analog in which the 2'-hydroxyl group hydrogen-bonding capacity has also been eliminated.
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Affiliation(s)
- G Moyna
- Department of Chemistry, Texas A&M University 77843-3255, USA
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Santander PJ, Roessner CA, Stolowich NJ, Holderman MT, Scott AI. How corrinoids are synthesized without oxygen: nature's first pathway to vitamin B12. Chem Biol 1997; 4:659-66. [PMID: 9331403 DOI: 10.1016/s1074-5521(97)90221-0] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
BACKGROUND During the biosynthesis of vitamin B12, the aerobic bacterium Pseudomonas denitrificans uses two enzymes, CobG and CobJ, to convert precorrin-3 to the ring-contracted intermediate, precorrin-4. CobG is a monooxygenase that adds a hydroxyl group, derived from molecular oxygen, to C-20, whereas CobJ is bifunctional, inserting a methyl group at C-17 of the macrocycle and catalyzing ring contraction. Molecular oxygen is not available to vitamin B12-producing anaerobic bacteria and members of the ancient Archaea, so the question arises of how these microbes accomplish the key ring-contraction process. RESULTS Cloning and overexpression of Salmonella typhimurium genes has led to the discovery that a single enzyme, CbiH, is responsible for ring contraction during anaerobic biosynthesis of vitamin B12. The process occurs when CbiH is incubated with precorrin-3, but only in the presence of cobalt. CbiH functions as a C-17 methyltransferase and mediates ring contraction and lactonization to yield the intermediate, cobalt-precorrin-4, isolated as cobalt-factor IV. 13C labeling studies have proved that cobalt-precorrin-4 is incorporated into cobyrinic acid, thereby confirming that cobalt-precorrin-4 is an intermediate in vitamin B12 biosynthesis. CONCLUSIONS Two distinct mechanisms exist in nature for the ring contraction of porphyrinoids to corrinoids-an ancient anaerobic pathway that requires cobalt complexation prior to nonoxidative rearrangement, and a more recent aerobic route in which molecular oxygen serves as the cofactor. The present results offer a rationale for the main differences between aerobic and anaerobic biosynthesis of vitamin B12. Thus, in anaerobes there is exchange of oxygen at the C-27 acetate site, extrusion of acetaldehyde and early insertion of cobalt, whereas the aerobes show no exchange of oxygen at C-27, extrude acetic acid and insert cobalt very late in the biosynthetic pathway, after ring contraction has occurred. These parallel routes to vitamin B12 have now been clearly distinguished by their differing mechanisms for ring contraction.
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Affiliation(s)
- P J Santander
- Chemistry Department, Texas A&M University, College Station 77843-3255, USA
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Moyna G, Hernandez G, Williams HJ, Nachman RJ, Scott AI. Development of Weiner et al. force field parameters suitable for conformational studies of [1,4]-benzodiazepines and related compounds. J Chem Inf Comput Sci 1997; 37:951-6. [PMID: 9316265 DOI: 10.1021/ci9700236] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A set of force field parameters capable of reproducing the preferred conformations of the biologically important [1,4]-benzodiazepines was developed for AMBER and other molecular modeling programs that utilize the Weiner et al. force field. Equilibrium parameters were obtained from representative model compounds found in the Cambridge Structural Database, and bond stretching and torsion potential force constants were estimated using AM1 and PM3 semiempirical Hamiltonians. Parameters obtained with the two semiempirical methods and the existing linear interpolation method are compared. Molecular mechanics and dynamic simulations showed that AM1 derived parameters, together with MNDO ESP fitted atomic charges, predicted the X-ray structure of a number of representative [1,4]-benzodiazepines within 0.01 A, 0.8 degree, and 5 degrees, from observed bond lengths, bond angles, and bond torsions, respectively.
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Affiliation(s)
- G Moyna
- Department of Chemistry, Texas A&M University, College Station 77843-3255, USA
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Scott AI. Treatment of postnatal depression. Two weeks of depression may not be long enough to exclude spontaneous recovery. BMJ 1997; 315:122. [PMID: 9240066 PMCID: PMC2127065 DOI: 10.1136/bmj.315.7100.122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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Glen T, Scott AI. Recent registration and referrals from general practitioners. Br J Psychiatry 1997; 170:288-9. [PMID: 9229041 DOI: 10.1192/bjp.170.3.288b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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