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Bou Ghanem A, Hussayni Y, Kadbey R, Ratel Y, Yehya S, Khouzami L, Ghadieh HE, Kanaan A, Azar S, Harb F. Exploring the complexities of 1C metabolism: implications in aging and neurodegenerative diseases. Front Aging Neurosci 2024; 15:1322419. [PMID: 38239489 PMCID: PMC10794399 DOI: 10.3389/fnagi.2023.1322419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Accepted: 12/11/2023] [Indexed: 01/22/2024] Open
Abstract
The intricate interplay of one-carbon metabolism (OCM) with various cellular processes has garnered substantial attention due to its fundamental implications in several biological processes. OCM serves as a pivotal hub for methyl group donation in vital biochemical reactions, influencing DNA methylation, protein synthesis, and redox balance. In the context of aging, OCM dysregulation can contribute to epigenetic modifications and aberrant redox states, accentuating cellular senescence and age-associated pathologies. Furthermore, OCM's intricate involvement in cancer progression is evident through its capacity to provide essential one-carbon units crucial for nucleotide synthesis and DNA methylation, thereby fueling uncontrolled cell proliferation and tumor development. In neurodegenerative disorders like Alzheimer's and Parkinson's, perturbations in OCM pathways are implicated in the dysregulation of neurotransmitter synthesis and mitochondrial dysfunction, contributing to disease pathophysiology. This review underscores the profound impact of OCM in diverse disease contexts, reinforcing the need for a comprehensive understanding of its molecular complexities to pave the way for targeted therapeutic interventions across inflammation, aging and neurodegenerative disorders.
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Affiliation(s)
- Ayman Bou Ghanem
- Faculty of Medicine and Medical Sciences, University of Balamand, Tripoli, Lebanon
| | - Yaman Hussayni
- Faculty of Medicine and Medical Sciences, University of Balamand, Tripoli, Lebanon
| | - Raghid Kadbey
- Faculty of Medicine and Medical Sciences, University of Balamand, Tripoli, Lebanon
| | - Yara Ratel
- Faculty of Medicine and Medical Sciences, University of Balamand, Tripoli, Lebanon
| | - Shereen Yehya
- Faculty of Medicine and Medical Sciences, University of Balamand, Tripoli, Lebanon
| | - Lara Khouzami
- College of Natural and Health Sciences, Zayed University, Dubai, United Arab Emirates
| | - Hilda E. Ghadieh
- Faculty of Medicine and Medical Sciences, University of Balamand, Tripoli, Lebanon
- AUB Diabetes, American University of Beirut Medical Center, Beirut, Lebanon
| | - Amjad Kanaan
- Faculty of Medicine and Medical Sciences, University of Balamand, Tripoli, Lebanon
| | - Sami Azar
- Faculty of Medicine and Medical Sciences, University of Balamand, Tripoli, Lebanon
| | - Frederic Harb
- Faculty of Medicine and Medical Sciences, University of Balamand, Tripoli, Lebanon
- AUB Diabetes, American University of Beirut Medical Center, Beirut, Lebanon
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2
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Froese DS, Fowler B, Baumgartner MR. Vitamin B 12 , folate, and the methionine remethylation cycle-biochemistry, pathways, and regulation. J Inherit Metab Dis 2019; 42:673-685. [PMID: 30693532 DOI: 10.1002/jimd.12009] [Citation(s) in RCA: 192] [Impact Index Per Article: 38.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Revised: 09/27/2018] [Accepted: 10/19/2018] [Indexed: 12/16/2022]
Abstract
Vitamin B12 (cobalamin, Cbl) is a nutrient essential to human health. Due to its complex structure and dual cofactor forms, Cbl undergoes a complicated series of absorptive and processing steps before serving as cofactor for the enzymes methylmalonyl-CoA mutase and methionine synthase. Methylmalonyl-CoA mutase is required for the catabolism of certain (branched-chain) amino acids into an anaplerotic substrate in the mitochondrion, and dysfunction of the enzyme itself or in production of its cofactor adenosyl-Cbl result in an inability to successfully undergo protein catabolism with concomitant mitochondrial energy disruption. Methionine synthase catalyzes the methyl-Cbl dependent (re)methylation of homocysteine to methionine within the methionine cycle; a reaction required to produce this essential amino acid and generate S-adenosylmethionine, the most important cellular methyl-donor. Disruption of methionine synthase has wide-ranging implications for all methylation-dependent reactions, including epigenetic modification, but also for the intracellular folate pathway, since methionine synthase uses 5-methyltetrahydrofolate as a one-carbon donor. Folate-bound one-carbon units are also required for deoxythymidine monophosphate and de novo purine synthesis; therefore, the flow of single carbon units to each of these pathways must be regulated based on cellular needs. This review provides an overview on Cbl metabolism with a brief description of absorption and intracellular metabolic pathways. It also provides a description of folate-mediated one-carbon metabolism and its intersection with Cbl at the methionine cycle. Finally, a summary of recent advances in understanding of how both pathways are regulated is presented.
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Affiliation(s)
- D Sean Froese
- Division of Metabolism and Children's Research Center, University Children's Hospital, Zurich, Switzerland
| | - Brian Fowler
- Division of Metabolism and Children's Research Center, University Children's Hospital, Zurich, Switzerland
| | - Matthias R Baumgartner
- Division of Metabolism and Children's Research Center, University Children's Hospital, Zurich, Switzerland
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3
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Abstract
Despite unequivocal evidence that folate deficiency increases risk for human pathologies, and that folic acid intake among women of childbearing age markedly decreases risk for birth defects, definitive evidence for a causal biochemical pathway linking folate to disease and birth defect etiology remains elusive. The de novo and salvage pathways for thymidylate synthesis translocate to the nucleus of mammalian cells during S- and G2/M-phases of the cell cycle and associate with the DNA replication and repair machinery, which limits uracil misincorporation into DNA and genome instability. There is increasing evidence that impairments in nuclear de novo thymidylate synthesis occur in many pathologies resulting from impairments in one-carbon metabolism. Understanding the roles and regulation of nuclear de novo thymidylate synthesis and its relationship to genome stability will increase our understanding of the fundamental mechanisms underlying folate- and vitamin B12-associated pathologies.
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Affiliation(s)
- Martha S Field
- Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853, USA;
| | - Elena Kamynina
- Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853, USA;
| | - James Chon
- Graduate Field of Biochemistry, Molecular, and Cell Biology, Cornell University, Ithaca, New York 14853, USA
| | - Patrick J Stover
- College of Agriculture and Life Sciences, Texas A&M University, College Station, Texas 77843-2142, USA;
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4
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Lan X, Field MS, Stover PJ. Cell cycle regulation of folate-mediated one-carbon metabolism. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2018; 10:e1426. [DOI: 10.1002/wsbm.1426] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 04/26/2018] [Accepted: 04/27/2018] [Indexed: 12/25/2022]
Affiliation(s)
- Xu Lan
- Division of Nutritional Sciences; Cornell University; Ithaca New York
| | - Martha S. Field
- Division of Nutritional Sciences; Cornell University; Ithaca New York
| | - Patrick J. Stover
- Division of Nutritional Sciences; Cornell University; Ithaca New York
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5
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Abstract
Protein modification with the small ubiquitin-related modifier (SUMO) can affect protein function, enzyme activity, protein-protein interactions, protein stability, protein targeting and cellular localization. SUMO influences the function and regulation of metabolic enzymes within pathways, and in some cases targets entire metabolic pathways by affecting the activity of transcription factors or by facilitating the translocation of entire metabolic pathways to subcellular compartments. SUMO modification is also a key component of nutrient- and metabolic-sensing mechanisms that regulate cellular metabolism. In addition to its established roles in maintaining metabolic homeostasis, there is increasing evidence that SUMO is a key factor in facilitating cellular stress responses through the regulation and/or adaptation of the most fundamental metabolic processes, including energy and nucleotide metabolism. This review focuses on the role of SUMO in cellular metabolism and metabolic disease.
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6
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Abstract
Nonalcoholic fatty liver disease (NAFLD) is a spectrum of chronic liver conditions that are characterized by steatosis, inflammation, fibrosis, and liver injury. The global prevalence of NAFLD is rapidly increasing in proportion to the rising incidence of obesity and type 2 diabetes. Because NAFLD is a multifaceted disorder with many underlying metabolic abnormalities, currently, there is no pharmacological agent that is therapeutically approved for the treatment of this disease. Folate is a water-soluble B vitamin that plays an essential role in one-carbon transfer reactions involved in nucleic acid biosynthesis, methylation reactions, and sulfur-containing amino acid metabolism. The liver is the primary organ responsible for storage and metabolism of folates. Low serum folate levels have been observed in patients with obesity and diabetes. It has been reported that a low level of endogenous folates in rodents perturbs folate-dependent one-carbon metabolism, and may be associated with development of metabolic diseases such as NAFLD. This review highlights the biological role of folate in the progression of NAFLD and its associated metabolic complications including obesity and type 2 diabetes. Understanding the role of folate in metabolic disease may position this vitamin as a potential therapeutic for NAFLD.
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Affiliation(s)
- Victoria Sid
- a St. Boniface Hospital Albrechtsen Research Centre, Winnipeg, MB R2H 2A6, Canada.,b Department of Physiology and Pathophysiology, University of Manitoba, Winnipeg, MB R3E 0J9, Canada
| | - Yaw L Siow
- a St. Boniface Hospital Albrechtsen Research Centre, Winnipeg, MB R2H 2A6, Canada.,b Department of Physiology and Pathophysiology, University of Manitoba, Winnipeg, MB R3E 0J9, Canada.,c Agriculture and Agri-Food Canada, Winnipeg, MB R3C 1B2, Canada
| | - Karmin O
- a St. Boniface Hospital Albrechtsen Research Centre, Winnipeg, MB R2H 2A6, Canada.,b Department of Physiology and Pathophysiology, University of Manitoba, Winnipeg, MB R3E 0J9, Canada.,d Department of Animal Science, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
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7
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Folates as adjuvants to anticancer agents: Chemical rationale and mechanism of action. Crit Rev Oncol Hematol 2016; 106:118-31. [PMID: 27637357 DOI: 10.1016/j.critrevonc.2016.08.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 07/01/2016] [Accepted: 08/09/2016] [Indexed: 12/31/2022] Open
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Naz N, Jimenez AR, Sanjuan-Vilaplana A, Gurney M, Miyan J. Neonatal hydrocephalus is a result of a block in folate handling and metabolism involving 10-formyltetrahydrofolate dehydrogenase. J Neurochem 2016; 138:610-23. [DOI: 10.1111/jnc.13686] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 04/29/2016] [Accepted: 05/23/2016] [Indexed: 11/30/2022]
Affiliation(s)
- Naila Naz
- Faculty of Life Sciences; The University of Manchester; Manchester UK
| | | | | | - Megan Gurney
- Faculty of Life Sciences; The University of Manchester; Manchester UK
| | - Jaleel Miyan
- Faculty of Life Sciences; The University of Manchester; Manchester UK
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9
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Fernández-Murray JP, Prykhozhij SV, Dufay JN, Steele SL, Gaston D, Nasrallah GK, Coombs AJ, Liwski RS, Fernandez CV, Berman JN, McMaster CR. Glycine and Folate Ameliorate Models of Congenital Sideroblastic Anemia. PLoS Genet 2016; 12:e1005783. [PMID: 26821380 PMCID: PMC4731144 DOI: 10.1371/journal.pgen.1005783] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Accepted: 12/11/2015] [Indexed: 01/25/2023] Open
Abstract
Sideroblastic anemias are acquired or inherited anemias that result in a decreased ability to synthesize hemoglobin in red blood cells and result in the presence of iron deposits in the mitochondria of red blood cell precursors. A common subtype of congenital sideroblastic anemia is due to autosomal recessive mutations in the SLC25A38 gene. The current treatment for SLC25A38 congenital sideroblastic anemia is chronic blood transfusion coupled with iron chelation. The function of SLC25A38 is not known. Here we report that the SLC25A38 protein, and its yeast homolog Hem25, are mitochondrial glycine transporters required for the initiation of heme synthesis. To do so, we took advantage of the fact that mitochondrial glycine has several roles beyond the synthesis of heme, including the synthesis of folate derivatives through the glycine cleavage system. The data were consistent with Hem25 not being the sole mitochondrial glycine importer, and we identify a second SLC25 family member Ymc1, as a potential secondary mitochondrial glycine importer. Based on these findings, we observed that high levels of exogenous glycine, or 5-aminolevulinic acid (5-Ala) a metabolite downstream of Hem25 in heme biosynthetic pathway, were able to restore heme levels to normal in yeast cells lacking Hem25 function. While neither glycine nor 5-Ala could ameliorate SLC25A38 congenital sideroblastic anemia in a zebrafish model, we determined that the addition of folate with glycine was able to restore hemoglobin levels. This difference is likely due to the fact that yeast can synthesize folate, whereas in zebrafish folate is an essential vitamin that must be obtained exogenously. Given the tolerability of glycine and folate in humans, this study points to a potential novel treatment for SLC25A38 congenital sideroblastic anemia. Mutations in the SLC25A38 gene cause an inherited anemia. In this study we determine that the function of SLC25A38, and its yeast homolgue Hem25, is to act as mitochondrial glycine importers providing a molecular explanation for why patients with SLC25A38 mutations have low hemoglobin levels and become anemic. Using this new knowledge, we go on to determine that supplementation with glycine and folate restore hemoglobin levels in a zebrafish model of the disease pointing to a potentially new, safe, and cost effective treatment for SLC25A38 congenital sideroblastic anemia.
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Affiliation(s)
| | - Sergey V. Prykhozhij
- Department of Pediatrics, IWK Health Centre, Dalhousie University, Halifax, Canada
| | - J. Noelia Dufay
- Department of Pharmacology, Dalhousie University, Halifax, Canada
| | - Shelby L. Steele
- Department of Pediatrics, IWK Health Centre, Dalhousie University, Halifax, Canada
| | - Daniel Gaston
- Department of Pathology, Dalhousie University, Halifax, Canada
| | | | - Andrew J. Coombs
- Department of Pediatrics, IWK Health Centre, Dalhousie University, Halifax, Canada
| | | | - Conrad V. Fernandez
- Department of Pediatrics, IWK Health Centre, Dalhousie University, Halifax, Canada
| | - Jason N. Berman
- Department of Pediatrics, IWK Health Centre, Dalhousie University, Halifax, Canada
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Bailey LB, Stover PJ, McNulty H, Fenech MF, Gregory JF, Mills JL, Pfeiffer CM, Fazili Z, Zhang M, Ueland PM, Molloy AM, Caudill MA, Shane B, Berry RJ, Bailey RL, Hausman DB, Raghavan R, Raiten DJ. Biomarkers of Nutrition for Development-Folate Review. J Nutr 2015; 145:1636S-1680S. [PMID: 26451605 PMCID: PMC4478945 DOI: 10.3945/jn.114.206599] [Citation(s) in RCA: 296] [Impact Index Per Article: 32.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Revised: 12/11/2014] [Accepted: 04/14/2015] [Indexed: 12/13/2022] Open
Abstract
The Biomarkers of Nutrition for Development (BOND) project is designed to provide evidence-based advice to anyone with an interest in the role of nutrition in health. Specifically, the BOND program provides state-of-the-art information and service with regard to selection, use, and interpretation of biomarkers of nutrient exposure, status, function, and effect. To accomplish this objective, expert panels are recruited to evaluate the literature and to draft comprehensive reports on the current state of the art with regard to specific nutrient biology and available biomarkers for assessing nutrients in body tissues at the individual and population level. Phase I of the BOND project includes the evaluation of biomarkers for 6 nutrients: iodine, iron, zinc, folate, vitamin A, and vitamin B-12. This review represents the second in the series of reviews and covers all relevant aspects of folate biology and biomarkers. The article is organized to provide the reader with a full appreciation of folate's history as a public health issue, its biology, and an overview of available biomarkers (serum folate, RBC folate, and plasma homocysteine concentrations) and their interpretation across a range of clinical and population-based uses. The article also includes a list of priority research needs for advancing the area of folate biomarkers related to nutritional health status and development.
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Affiliation(s)
- Lynn B Bailey
- Department of Foods and Nutrition, University of Georgia, Athens, GA;
| | - Patrick J Stover
- Division of Nutritional Sciences, Cornell University, Ithaca, NY
| | - Helene McNulty
- Northern Ireland Centre for Food and Health, Biomedical Sciences Research Institute, University of Ulster, Londonderry, United Kingdom
| | - Michael F Fenech
- Genome Health Nutrigenomics Laboratory, Food, Nutrition, and Bioproducts Flagship, Commonwealth Scientific and Industrial Research Organization, Adelaide, Australia
| | - Jesse F Gregory
- Food Science and Human Nutrition Department, University of Florida, Gainesville, FL
| | - James L Mills
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD
| | | | - Zia Fazili
- National Center for Environmental Health, CDC, Atlanta, GA
| | - Mindy Zhang
- National Center for Environmental Health, CDC, Atlanta, GA
| | - Per M Ueland
- Department of Clinical Science, Univeristy of Bergen, Bergen, Norway
| | - Anne M Molloy
- Institute of Molecular Medicine, Trinity College, Dublin, Ireland
| | - Marie A Caudill
- Division of Nutritional Sciences, Cornell University, Ithaca, NY
| | - Barry Shane
- Department of Nutritional Sciences and Toxicology, University of California-Berkeley, Berkeley, CA
| | - Robert J Berry
- National Center on Birth Defects and Developmental Disabilities, CDC, Atlanta, GA; and
| | | | - Dorothy B Hausman
- Department of Foods and Nutrition, University of Georgia, Athens, GA
| | - Ramkripa Raghavan
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD
| | - Daniel J Raiten
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD;
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Scotti M, Stella L, Shearer EJ, Stover PJ. Modeling cellular compartmentation in one-carbon metabolism. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2013; 5:343-65. [PMID: 23408533 DOI: 10.1002/wsbm.1209] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Folate-mediated one-carbon metabolism (FOCM) is associated with risk for numerous pathological states including birth defects, cancers, and chronic diseases. Although the enzymes that constitute the biological pathways have been well described and their interdependency through the shared use of folate cofactors appreciated, the biological mechanisms underlying disease etiologies remain elusive. The FOCM network is highly sensitive to nutritional status of several B-vitamins and numerous penetrant gene variants that alter network outputs, but current computational approaches do not fully capture the dynamics and stochastic noise of the system. Combining the stochastic approach with a rule-based representation will help model the intrinsic noise displayed by FOCM, address the limited flexibility of standard simulation methods for coarse-graining the FOCM-associated biochemical processes, and manage the combinatorial complexity emerging from reactions within FOCM that would otherwise be intractable.
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Affiliation(s)
- Marco Scotti
- The Microsoft Research-University of Trento Centre for Computational and Systems Biology (COSBI), Rovereto, Italy
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12
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Abstract
The role of metabolic compartmentation in spatially organizing metabolic enzymes into pathways, regulating flux through metabolic pathways, and controlling the partitioning of metabolic intermediates among pathways is appreciated, but our understanding of the mechanisms that establish metabolic architecture and mediate communication and regulation among interconnected metabolic pathways and networks is still incomplete. This review discusses recent advancements in our understanding of metabolic compartmentation within the pathways that constitute the folate-mediated one-carbon metabolic network and emerging evidence for a need to regulate the trafficking of folates among compartmentalized metabolic pathways.
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13
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Luka Z, Moss F, Loukachevitch LV, Bornhop DJ, Wagner C. Histone demethylase LSD1 is a folate-binding protein. Biochemistry 2011; 50:4750-6. [PMID: 21510664 DOI: 10.1021/bi200247b] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Methylation of lysine residues in histones has been known to serve a regulatory role in gene expression. Although enzymatic removal of the methyl groups was discovered as early as 1973, the enzymes responsible for their removal were isolated and their mechanism of action was described only recently. The first enzyme to show such activity was LSD1, a flavin-containing enzyme that removes the methyl groups from lysines 4 and 9 of histone 3 with the generation of formaldehyde from the methyl group. This reaction is similar to the previously described demethylation reactions conducted by the enzymes dimethylglycine dehydrogenase and sarcosine dehydrogenase, in which protein-bound tetrahydrofolate serves as an accepter of the formaldehyde that is generated. We now show that nuclear extracts of HeLa cells contain LSD1 that is associated with folate. Using the method of back-scattering interferometry, we have measured the binding of various forms of folate to both full-length LSD1 and a truncated form of LSD1 in free solution. The 6R,S form of the natural pentaglutamate form of tetrahydrofolate bound with the highest affinity (K(d) = 2.8 μM) to full-length LSD1. The fact that folate participates in the enzymatic demethylation of histones provides an opportunity for this micronutrient to play a role in the epigenetic control of gene expression.
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Affiliation(s)
- Zigmund Luka
- Department of Biochemistry, Vanderbilt University Medical Center, Nashville, TN 37232, USA
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14
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Tibbetts AS, Appling DR. Compartmentalization of Mammalian folate-mediated one-carbon metabolism. Annu Rev Nutr 2010; 30:57-81. [PMID: 20645850 DOI: 10.1146/annurev.nutr.012809.104810] [Citation(s) in RCA: 488] [Impact Index Per Article: 34.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The recognition that mitochondria participate in folate-mediated one-carbon metabolism grew out of pioneering work beginning in the 1950s from the laboratories of D.M. Greenberg, C.G. Mackenzie, and G. Kikuchi. These studies revealed mitochondria as the site of oxidation of one-carbon donors such as serine, glycine, sarcosine, and dimethylglycine. Subsequent work from these laboratories and others demonstrated the participation of folate coenzymes and folate-dependent enzymes in these mitochondrial processes. Biochemical and molecular genetic approaches in the 1980s and 1990s identified many of the enzymes involved and revealed an interdependence of cytoplasmic and mitochondrial one-carbon metabolism. These studies led to the development of a model of eukaryotic one-carbon metabolism that comprises parallel cytosolic and mitochondrial pathways, connected by one-carbon donors such as serine, glycine, and formate. Sequencing of the human and other mammalian genomes has facilitated identification of the enzymes that participate in this intercompartmental one-carbon metabolism, and animal models are beginning to clarify the roles of the cytoplasmic and mitochondrial isozymes of these enzymes. Identifying the mitochondrial transporters for the one-carbon donors and elucidating how flux through these pathways is controlled are two areas ripe for exploration.
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Affiliation(s)
- Anne S Tibbetts
- Department of Chemistry and Biochemistry, and the Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA
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15
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Abstract
Impairments in folate-mediated 1-carbon metabolism are associated with several common diseases and developmental anomalies including intestinal cancers, vascular disease, cognitive decline, and neural tube defects. The etiology of folate-associated pathologies involves interactions among multiple genetic risk alleles and environmental factors, although the causal mechanisms that define the role of folate and other B-vitamins in these complex disorders remain to be established. Folate and other B-vitamins fundamentally differ from other nutrients that interact with the genome in determining health and disease outcomes in that their interaction is reciprocal. Common gene variants influence the activity of folate-dependent enzymes and anabolic pathways; folate-mediated 1-carbon metabolism is essential for the high-fidelity synthesis of DNA and activated methyl groups that are required for DNA methylation and regulation of chromatin structure. This review focuses on the regulation of folate-mediated 1-carbon metabolism and its role in maintaining genome integrity and on strategies for establishing the metabolic pathways and mechanisms that underlie folate-associated pathologies.
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Affiliation(s)
- Patrick J Stover
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA.
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16
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Anderson DD, Stover PJ. SHMT1 and SHMT2 are functionally redundant in nuclear de novo thymidylate biosynthesis. PLoS One 2009; 4:e5839. [PMID: 19513116 PMCID: PMC2688753 DOI: 10.1371/journal.pone.0005839] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2009] [Accepted: 04/30/2009] [Indexed: 11/23/2022] Open
Abstract
The three enzymes that constitute the de novo thymidylate synthesis pathway in mammals, cytoplasmic serine hydroxymethyltransferase (SHMT1), thymidylate synthase (TYMS) and dihydrofolate reductase (DHFR) undergo sumoylation and nuclear import during S-phase. In this study, we demonstrate that purified intact mouse liver nuclei convert dUMP to dTMP in the presence of NADPH and serine. Neither nuclear extracts nor intact nuclei exposed to aminomethylphosphonate, a SHMT inhibitor, exhibit thymidylate synthesis activity. Nuclei isolated from Shmt1(-/-) mouse livers retained 25% of thymidylate synthesis activity exhibited by nuclei isolated from wild type mice. This residual activity was due to the presence of a cytoplasmic/nuclear isozyme of SHMT encoded by Shmt2. Shmt2 is shown to encode two transcripts, one which encodes a protein that localizes exclusively to the mitochondria (SHMT2), and a second transcript that lacks exon 1 and encodes a protein that localizes to the cytoplasm and nucleus during S-phase (SHMT2alpha). The ability of Shmt2 to encode a cytoplasmic isozyme of SHMT may account for the viability of Shmt1(-/-) mice and provide redundancy that permitted the expansion of the human SHMT1 L474F polymorphism that impairs SHMT1 sumoylation and nuclear translocation.
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Affiliation(s)
- Donald D. Anderson
- Graduate Field of Biochemistry, Molecular and Cellular Biology, Cornell University, Ithaca, New York, United States of America
| | - Patrick J. Stover
- Graduate Field of Biochemistry, Molecular and Cellular Biology, Cornell University, Ithaca, New York, United States of America
- Division of Nutritional Sciences, Cornell University, Ithaca, New York, United States of America
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17
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Stover PJ, MacFarlane AJ. Mouse models to elucidate mechanisms of folate-related cancer pathologies. Nutr Rev 2009; 66 Suppl 1:S54-8. [PMID: 18673492 DOI: 10.1111/j.1753-4887.2008.00069.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Affiliation(s)
- Patrick J Stover
- Cornell University, Division of Nutritional Sciences, Ithaca, New York 14853, USA.
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18
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Woeller CF, Anderson DD, Szebenyi DME, Stover PJ. Evidence for small ubiquitin-like modifier-dependent nuclear import of the thymidylate biosynthesis pathway. J Biol Chem 2007; 282:17623-31. [PMID: 17446168 DOI: 10.1074/jbc.m702526200] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Perturbations in folate-mediated one-carbon metabolism increase rates of uracil misincorporation into DNA during replication, impair cellular methylation reactions, and increase risk for neural tube defects and cancer. One-carbon metabolism is compromised by folate deficiency and common genetic polymorphisms. In this study, the mechanism for the preferential partitioning of cytoplasmic serine hydroxymethyltransferase (cSHMT)-derived methylenetetrahydrofolate to de novo thymidylate biosynthesis was investigated. The cSHMT enzyme was shown to interact with UBC9 and was a substrate for UBC9-catalyzed small ubiquitin-like modifier (SUMO) modification in vitro. SUMOylated cSHMT was detected in extracts from S phase MCF-7 cells, and cSHMT was shown to localize to the nucleus and nuclear periphery during the S and G(2)/M phases of the cell cycle. A common single nucleotide polymorphism (L474F-cSHMT) impaired the UBC9-cSHMT interaction and inhibited cSHMT SUMOylation in vitro. The three folate-dependent enzymes that constitute the de novo thymidylate biosynthesis pathway, cSHMT, thymidylate synthase, and dihydrofolate reductase, all contain SUMO modification consensus sequences. Compartmentation of the folate-dependent de novo thymidylate biosynthesis pathway in the nucleus accounts for the preferential partitioning of cSHMT-derived folate-activated one-carbon units into thymidylate biosynthesis; the efficiency of nuclear folate metabolism is likely to be modified by the cSHMT L474F polymorphism.
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Affiliation(s)
- Collynn F Woeller
- Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853, USA
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Small ubiquitin-like modifier-1 (SUMO-1) modification of thymidylate synthase and dihydrofolate reductase. ACTA ACUST UNITED AC 2007; 45:1760-3. [DOI: 10.1515/cclm.2007.355] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
AbstractClin Chem Lab Med 2007;45:1760–3.
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Baggott JE, MacKenzie RE. 5,10-methenyltetrahydrofolate cyclohydrolase, rat liver and chemically catalysed formation of 5-formyltetrahydrofolate. Biochem J 2003; 374:773-8. [PMID: 12793858 PMCID: PMC1223631 DOI: 10.1042/bj20021970] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2002] [Revised: 06/02/2003] [Accepted: 06/09/2003] [Indexed: 11/17/2022]
Abstract
The 5,10-methenyltetrahydrofolate (5,10-CH=H4folate) synthetase catalyses the physiologically irreversible formation of 5,10-CH=H4folate from 5-formyltetrahydrofolate (5-HCO-H4folate) and ATP. It is not clear how (or if) 5-HCO-H4folate is formed in vivo. Using a spectrophotometric assay for 5-HCO-H4folate, human recombinant 5,10-CH=H4folate cyclohydrolase, which catalyses the hydrolysis of 5,10-CH=H4folate to 10-HCO-H4folate, was previously shown to catalyse inefficiently the formation of 5-HCO-H4folate at pH 7.3 [Pelletier and MacKenzie (1996) Bioorg. Chem. 24, 220-228]. In the present study, we report that (i) the human cyclohydrolase enzyme catalyses the conversion of 10-HCO-/5,10-CH=H4folate into 5-HCO-H4folate (it is also chemically formed) at pH 4.0-7.0; (ii) rat liver has a very low capacity to catalyse the formation of 5-HCO-H4folate when compared with the traditional activity of 5,10-CH=H4folate cyclohydrolase and the activity of the 5,10-CH=H4folate synthetase; and (iii) a substantial amount of 5-HCO-H4folate reported to be present in rat liver is chemically formed during analytical procedures. We conclude that (i) the cyclohydrolase represents some of the capacity of rat liver to catalyse the formation of 5-HCO-H4folate; (ii) the amount of 5-HCO-H4folate reported to be present in rat liver is overestimated (liver 5-HCO-H4folate content may be negligible); and (iii) there is little evidence that 5-HCO-H4folate inhibits one-carbon metabolism in mammals.
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Affiliation(s)
- Joseph E Baggott
- Department of Nutrition Sciences, University of Alabama at Birmingham, Birmingham, AL 35294-3360, USA
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21
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Han YH, Kato Y, Kusuhara H, Suzuki H, Shimoda M, Kokue E, Sugiyama Y. Kinetic profile of overall elimination of 5-methyltetrahydropteroylglutamate in rats. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:E580-7. [PMID: 10070027 DOI: 10.1152/ajpendo.1999.276.3.e580] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The in vivo biliary and urinary excretion kinetics of 5-methyltetrahydropteroylglutamate (5-CH3-H4PteGlu) were studied in rats. During infusion at various rates (48-965 nmol. h-1. kg-1), the total body clearance (CLtotal) of 5-CH3-H4PteGlu could be attributed almost entirely to the sum of the biliary and urinary (CLurine,p) excretion clearances. After a 4-h infusion at the highest rate, the 5-CH3-H4PteGlu in the liver was 10 times higher than the endogenous level, whereas its polyglutamate form did not increase, suggesting that most of the infused 5-CH3-H4PteGlu is not incorporated in the polyglutamate pool but is eliminated by excretion. The parallel increase in CLtotal and CLurine,p with the increase in infusion rate might result from saturation of reabsorption at the renal proximal tubules, since the urinary excretion clearance, defined with respect to the kidney concentration, also increased while the biliary excretion clearance, defined with respect to the liver concentration, remained almost constant. We conclude that the hepatobiliary excretion is a relatively low-affinity process with a constant clearance, whereas the renal tubular reabsorption is saturated at higher plasma 5-CH3-H4PteGlu concentration ( approximately 0.5 microM). Urinary excretion becomes the predominant elimination route for any excess 5-CH3-H4PteGlu in the body.
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Affiliation(s)
- Y H Han
- Graduate School of Pharmaceutical Sciences, University of Tokyo, Hongo, Tokyo 113-0033, Japan
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22
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Horne DW, Holloway RS. Compartmentation of folate metabolism in rat pancreas: nitrous oxide inactivation of methionine synthase leads to accumulation of 5-methyltetrahydrofolate in cytosol. J Nutr 1997; 127:1772-5. [PMID: 9278558 DOI: 10.1093/jn/127.9.1772] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Folate-dependent one-carbon metabolism and methylation reactions have been implicated in the secretory function of the pancreas. Because vitamin B-12 deficiency perturbs folate metabolism, we determined the effects of nitrous oxide inactivation of methionine synthase on the compartmentation of folate metabolism in rat pancreas. Rats were exposed to an atmosphere of nitrous oxide and oxygen (80 and 20%, respectively) for 18 h; control rats breathed air. Folate coenzyme concentrations were determined by HPLC and Lactobacillus casei microbiological assay of the cytosolic and mitochondrial fractions of pancreas, which contained 62 and 46%, respectively, of the total folate. In pancreas of control rats, cytosolic folates were 5-methyltetrahydrofolate (31% of total folates), tetrahydrofolate (54%) and 5- and 10-formyltetrahydrofolate (6 and 8%, respectively). In the rats exposed to nitrous oxide, cytosolic 5-methyltetrahydrofolate concentrations were significantly greater (59% of total folates) and tetrahydrofolate concentrations were significantly lower (32%) than in controls; however, total cytosolic folate levels were unaffected by nitrous oxide exposure. In controls, mitochondrial folates were composed of 5-methyltetrahydrofolate (9% of total folates), tetrahydrofolate (60%) and 5- and 10-formyltetrahydrofolate (22 and 10%, respectively). Exposure to nitrous oxide led to significantly lower total mitochondrial folates (1.49 +/- 0.18 vs. 0.75 +/- 0.29 nmol/g, control vs. nitrous oxide, P < 0.05). This was due to a significantly lower concentration of tetrahydrofolate and 5-formyltetrahydrofolate, but not of 5-methyl- or 10-formyltetrahydrofolate. The activity of methionine synthase was 85% lower (P < 0.001) in pancreatic extracts of rats exposed to nitrous oxide than in controls. These results show that cytosolic folates accumulate in pancreas as the 5-methyl derivative at the expense of other reduced folates, as happens in liver. However, in contrast to results in liver, the mitochondrial folate concentration was lower in the pancreas of rats exposed to nitrous oxide, and this decline was limited to the 5-formyl- and tetrahydrofolate derivatives.
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Affiliation(s)
- D W Horne
- Biochemistry Research Laboratory (151), Department of Veterans Affairs Medical Center, Nashville, TN 37212-2637, USA
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23
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Lin B, Shane B. Expression of Escherichia coli folylpolyglutamate synthetase in the Chinese hamster ovary cell mitochondrion. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)36940-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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24
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Lin B, Huang R, Shane B. Regulation of folate and one-carbon metabolism in mammalian cells. III. Role of mitochondrial folylpoly-gamma-glutamate synthetase. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(20)80594-8] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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25
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García-Martínez LF, Appling DR. Characterization of the folate-dependent mitochondrial oxidation of carbon 3 of serine. Biochemistry 1993; 32:4671-6. [PMID: 8485144 DOI: 10.1021/bi00068a027] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The folate-dependent catabolism of serine was studied in intact rat liver mitochondria and soluble extracts from sonicated mitochondria. Formate and CO2 are both known to be products of the mitochondrial oxidation of carbon 3 of serine. The present work tests the proposal [Barlowe, C. K., & Appling, D. R. (1988) Biofactors 1, 171-176] that carbon 3 of serine is first oxidized to 10-formyltetrahydrofolate, which can be either oxidized to CO2 or converted to formate. Oxidation of carbon 3 of serine to formate and CO2 was shown to be dependent on the respiratory state of the mitochondria. Formate production was greatest in state-3 (actively respiring) mitochondria and lowest in uncoupled mitochondria. In contrast, CO2 production was greatest in uncoupled mitochondria and lowest in respiratory-inhibited mitochondria. Formate production appeared to be favored when high concentrations of NADP+ and ADP were present, but there was no clear correlation between the NADP+:NADPH redox state and CO2 production. In soluble mitochondrial extracts, CO2 production depended on NADP+ and tetrahydrofolate, whereas formate production required ADP in addition to NADP+ and the reduced folate cofactor. Unlike CO2 production, however, formate production showed a complete dependence on a polyglutamylated form of the folate cofactor. These experiments support the proposed folate-mediated serine oxidation as a major pathway for the flux of one-carbon units through mitochondria.
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Ng KY, Heath TD. Liposome-dependent delivery of pteridine antifolates: a two-compartment growth inhibition assay for evaluating drug leakage and metabolism. BIOCHIMICA ET BIOPHYSICA ACTA 1989; 981:261-8. [PMID: 2730904 DOI: 10.1016/0005-2736(89)90036-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
We have developed a two-compartment growth inhibition assay that can provide information about leakage, metabolism and delivery of liposome-dependent drugs under cell culture conditions, and at drug concentrations that are relevant to drug delivery. Two cell lines are grown in separate compartments separated from each other by a 0.1 micron polycarbonate membrane. The membrane allows free drugs to diffuse rapidly from one compartment to another, and does not allow liposomes to diffuse through. Liposomes are added to the first compartment, which contains target cells. The extent of leakage caused by these cells is determined by the growth inhibition of non-target cells in the second compartment. We show that methotrexate and methotrexate-gamma-aspartate leak rapidly and almost completely when encapsulated in phosphatidylglycerol/cholesterol (67:33) liposomes. In contrast, there is only 42% leakage when the drugs are encapsulated in distearoylphosphatidylglycerol/cholesterol (67:33) liposomes. We also demonstrate that the target cells (CV1-P) may partially degrade encapsulated methotrexate-gamma-aspartate to methotrexate. Therefore, methotrexate-gamma-aspartate may be a lysosomally cleaved pro-drug of methotrexate.
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Affiliation(s)
- K Y Ng
- School of Pharmacy, University of Wisconsin, Madison 53706
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27
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Horne DW, Patterson D, Cook RJ. Effect of nitrous oxide inactivation of vitamin B12-dependent methionine synthetase on the subcellular distribution of folate coenzymes in rat liver. Arch Biochem Biophys 1989; 270:729-33. [PMID: 2705787 DOI: 10.1016/0003-9861(89)90556-0] [Citation(s) in RCA: 88] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The effects of nitrous oxide inactivation of the vitamin B12-dependent enzyme, methionine synthetase (EC 2.1.1.13), on the subcellular distribution of hepatic folate coenzymes was determined. In controls, cytosolic folates were 5-methyltetrahydrofolate (45%), 5- and 10-formyltetrahydrofolate (9 and 19%, respectively), and tetrahydrofolate (27%). Exposure of rats to an atmosphere containing 80% nitrous oxide for 18 h resulted in a marked shift in this distribution pattern to 5-methyltetrahydrofolate, 84%; 5- and 10-formyltetrahydrofolate, 2.1 and 9.1%, respectively; and tetrahydrofolate, 4.7%. Activity of the cytosolic enzyme, methionine synthetase, was reduced by about 84% as compared to that of air breathing controls. In controls, mitochondrial folates were 5-methyltetrahydrofolate (7.3%), 5- and 10-formyltetrahydrofolate (11.5 and 33.1%, respectively), and tetrahydrofolate (48.1%). This distribution did not change after exposure to nitrous oxide. These results show that the effects of nitrous oxide inactivation of vitamin B12 are confined to the cytosol, at least in the short term, and suggest that there is little, if any, transport of free folates between the cytosolic and mitochondrial compartments.
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Affiliation(s)
- D W Horne
- Biochemistry Research Laboratory, Veterans Administration Medical Center, Nashville, Tennessee 37212-2637
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Shane B. Folylpolyglutamate synthesis and role in the regulation of one-carbon metabolism. VITAMINS AND HORMONES 1989; 45:263-335. [PMID: 2688305 DOI: 10.1016/s0083-6729(08)60397-0] [Citation(s) in RCA: 232] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The physiological importance of folylpolyglutamates is now well established. These derivatives are the intracellular substrates and regulators of one-carbon metabolism, and their synthesis is required for normal folate retention by tissues. Over the last few years, a considerable amount of information has been obtained on the mechanism by which these compounds are synthesized, on how this synthesis is regulated, and on the effects of the polyglutamate chain on the interaction of folate substrates and inhibitors with folate-dependent enzymes. Many regulatory implications have been suggested by these studies, but the physiological relevance of some of these observations remains to be explored. Folates in mammalian tissues are metabolized to polyglutamates of chain lengths considerably longer than that required for folate retention, but the metabolic advantages of this are not entirely clear. Several in vivo model systems have been developed to explore the functioning of specific folylpolyglutamate chain lengths in metabolic cycles of one-carbon metabolism, and these are likely to shed further light on this point. The role of folate-binding proteins in folate transport, the metabolic role of glutamylhydrolases, and the role of folylpolyglutamates in putative multifunctional protein complexes are also areas that are being actively pursued at present and are likely to produce new insights in the future. Recent studies on the retention of antifolates by cells and on their substrate efficacy for folylpolyglutamate synthetases have also suggested mechanisms for the differential cytotoxicity of these agents for different tissues.
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Case GL, Kaisaki PJ, Steele RD. Resolution of rat liver 10-formyltetrahydrofolate dehydrogenase/hydrolase activities. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(19)81498-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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30
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Purification and characterization of a mitochondrial isozyme of C1-tetrahydrofolate synthase from Saccharomyces cerevisiae. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(18)67234-5] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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31
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Finzi E, Beattie DS. The stimulation of yeast mitochondrial protein synthesis by low molecular weight cytoplasmic factors: requirement for intact mitochondria and lack of effect by folate derivatives. THE INTERNATIONAL JOURNAL OF BIOCHEMISTRY 1984; 16:177-82. [PMID: 6368283 DOI: 10.1016/0020-711x(84)90069-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Protein synthesis by GTP-supplemented yeast mitochondria is stimulated by a fraction of molecular weight less than 2,000 isolated from yeast high-speed supernatant (S-150). The low molecular weight fraction works independently of the respiratory chain as the stimulation effect is not cyanide-sensitive. Stimulation of mitochondrial protein synthesis by cytoplasmic factors is dependent upon the method of mitochondrial isolation. The low molecular weight stimulatory factor(s) are not reduced folate derivatives which supply formyl groups required for initiation of mitochondrial protein synthesis.
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32
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Taylor RT, Hanna ML. Folate-dependent enzymes in cultured Chinese hamster ovary cells: impaired mitochondrial serine hydroxymethyltransferase activity in two additional glycine--auxotroph complementation classes. Arch Biochem Biophys 1982; 217:609-23. [PMID: 7138028 DOI: 10.1016/0003-9861(82)90543-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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33
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Cybulski RL, Fisher RR. Uptake of oxidized folates by rat liver mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA 1981; 646:329-33. [PMID: 7295718 DOI: 10.1016/0005-2736(81)90339-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Folate, dihydrofolate, and methotrexate are rapidly taken up by rat liver mitochondria. The apparent maximal matrix folate concentration is about 2.5-fold that of the suspending medium, whereas dihydrofolate and methotrexate equilibrate across the inner membrane. Fully reduced folates, including tetrahydrofolate, 5-methyltetrahydrofolate, and 5,10-methylenetetrahydrofolate penetrate only the intermembrane space. Addition of dihydrofolate or methotrexate effects a rapid release of pre-loaded folate, and external methotrexate promotes the release of pre-loaded dihydrofolate. The extent of dihydrofolate uptake is enhanced by addition of folate. These results suggest that oxidized folates are transported to the matrix by a carrier-mediated mechanism.
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Abstract
Derivatives of folic acid occur in nature predominantly as poly (gamma-glutamyl) derivatives containing 2-8 glutamate residues. The data regarding the function of these derivatives, and their biosynthesis by eucaryotic and procaryotic folylpolyglutamate synthetases, is reviewed. The most universal functions of folylpolyglutamates appear to be (a) as the actual cofactors in vivo for folate dependent enzymes, (b) as inhibitors of folate dependent enzymes for which they are not substrates, and (c) to increase retention of folates after they are transported into cells as monoglutamates. Folylpolyglutamates also have numerous specialized functions in specific organisms, e.g. as structural components of some coliphage, and as allosteric regulators in Neurospora crassa. A single enzyme appears responsible for synthesis of all polyglutamate derivatives, regardless of length. With the recent introduction of sensitive assays this folylpolyglutamate synthetase has begun to be characterized. Although procaryotic and eucaryotic synthetases have many dissimilar properties, both types catalyze the ATP-dependent addition of L-glutamate to the gamma-carboxyl of the glutamate present in the folate. Both types also require a monovalent cation and relatively high pH. The most significant differences between the two types are in their folate substrate specificity and the product lengths derived from various folates.
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35
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Chan PY, Cossins EA. Polyglutamylfolate synthesis in Neurospora crassa: changes in pool size following growth in glycine- and methionine-supplemented media. Arch Biochem Biophys 1980; 200:346-56. [PMID: 6449176 DOI: 10.1016/0003-9861(80)90364-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Shane B, Watson JE, Stokstad EL. Uptake and metabolism of [3H]folate by normal and by vitamin B-12- and methionine-deficient rats. BIOCHIMICA ET BIOPHYSICA ACTA 1977; 497:241-52. [PMID: 849481 DOI: 10.1016/0304-4165(77)90157-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The uptake of an injected dose of [3H]folic acid and its metabolism to pteroylpoly-gamma-glutamate forms by the livers and kidneys of vitamin B-12- and methionine-deficient and -supplemented rats were investigated. The initial hepatic uptake of the labeled folate dose was the same in deficient and supplemented animals, demonstrating no involvement of vitamin B-12 or methionine in folate transport. At longer time periods, a decreased hepatic net uptake of labeled folate was observed in the deficient animals compared to supplemented animals, and this was directly correlated with the decreased ability of the deficient animals to synthesize pteroylpolyglutamates. The absolute rate of loss of labeled pteroylmonoglutamate from liver was the same in deficient and supplemented animals. These data are best explained by a modification of the 'methyl trap' hypothesis for the interrelationship of vitamin B-12 and folate metabolism. Vitamin B-12 deficiency can lead to lowered levels of 5-methyltetrahydrofolate:homocysteine methyltransferase, creating a functional folate deficiency by 'trapping' an increased proportion of folate as the methyl derivative. In addition, as methyltetrahydrofolate is a poor substrate for folylpoly-gamma-glutamate synthetase, there is a decreased synthesis of pteroylpolyglutamates, the forms of the vitamin that are preferentially retained by tissues. This results in decreased tissue folate levels under conditions of vitamin B-12 deficiency. Vitamin B-12 and methionine deficiency had no significant effect on the distribution of endogenous pteroylpolyglutamates in rat liver and kidney, although total endogenous folate in rat liver was reduced by about 60%. The distribution of labeled pteroylpolyglutamates in rat liver and kidney 48 h after the tracer dose of [3H]folate closely resembled the endogenous distribution in these tissues.
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