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Burke KL, Jennings IG. The Effect of a Dietary Supplement Containing Rhamnan Sulfate from Monostroma nitidum on Carotid Atherosclerotic Plaque: A Case Series. Integr Med (Encinitas) 2024; 22:30-37. [PMID: 38404609 PMCID: PMC10886398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
We report on 6 patients in our care who were harboring atherosclerotic plaque in the carotid arteries. This condition poses a risk of acute ischemic stroke and indicates potential atherosclerosis elsewhere in the vascular system. The plaque was revealed by routine ultrasound measurement of carotid intima-medial thickness (CIMT) defined as the distance between the lumen-intima interface and the media-adventitia interface. Recent improvements in image resolution and edge detection algorithms have resulted in improved reliability and clinical usefulness of the technology. The patients were enrolled in a systems-based functional medicine program of cardiology prevention to address root causes. The program provided personalized interventions that included drug therapy, dietary supplements, and lifestyle modification. The 6 patients followed the integrative regimen, which successfully managed existing cardiovascular symptoms and risk factors while keeping various biomarkers under control. However, they continued to exhibit carotid plaque with no improvement. A novel dietary supplement that targets endothelial glycocalyx regeneration was added to the personalized intervention programs. The supplement contains a proprietary extract of rhamnan sulfate from the green seaweed Monostroma nitidum. The 6 participants consumed the supplement daily, and their plaque burden was measured after 6 months using the same CIMT technology. In every case, the total plaque burden was reduced, with an average reduction in the 6 patients of 5.55 mm, which is statistically significant. Significant reductions in maximum carotid plaque thickness were also observed at the end of the 6 months. The study suggests that rhamnan sulfate from Monostroma nitidum may provide a safe and effective intervention for reducing atherosclerotic plaque, and should be evaluated as an adjunct therapy for prevention and treatment of cardiovascular disease.
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Affiliation(s)
- Kristine L. Burke
- Corresponding author: Kristine L. Burke, MD, ABFM, ABoIM, IFMCP E-mail address:
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2
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Oh DH, Ma X, Hogg SJ, He J, Kearney C, Brasacchio D, Susanto O, Maher B, Jennings IG, Newbold A, Fraser P, Gruber E, Kats LM, Gregory GP, Johnstone RW, Thompson PE, Shortt J. Rationally designed chimeric PI3K-BET bromodomain inhibitors elicit curative responses in MYC-driven lymphoma. Proc Natl Acad Sci U S A 2023; 120:e2306414120. [PMID: 37643213 PMCID: PMC10483632 DOI: 10.1073/pnas.2306414120] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Accepted: 08/01/2023] [Indexed: 08/31/2023] Open
Abstract
Targeted inhibitors of bromodomain and extraterminal (BET)-bromodomains and phosphatidylinositol-3-kinase (PI3K) signaling demonstrate potent but self-limited antilymphoma activity as single agents in the context of cellular Myelocytomatosis (cMYC) oncogene-dysregulation. However, combined PI3K and BET inhibition imparts synergistic anticancer activity with the potential for more sustained disease responses due to the mutual antagonism of compensatory epigenetic and signaling networks. Here, we describe the mechanistic and therapeutic validation of rationally designed dual PI3K/BET bromodomain inhibitors, built by linkage of established PI3K and BET inhibitor pharmacophores. The lead candidate demonstrates high selectivity, nanomolar range cellular potency, and compelling in vivo efficacy, including curative responses in the aggressive Eµ-Myc lymphoma model. These studies further support the therapeutic strategy of combined PI3K and BET inhibition and provide a potential step-change in approach to orthogonal MYC antagonism using optimized chimeric small-molecule technology.
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Affiliation(s)
- Danielle H. Oh
- Blood Cancer Therapeutics Laboratory, School of Clinical Sciences at Monash Health, Faculty of Medicine Nursing and Health Sciences, Monash University, MelbourneVIC3168, Australia
- Monash Haematology, Monash Health, MelbourneVIC3168, Australia
- Cancer Biology Therapeutics Program, Peter MacCallum Cancer Centre, MelbourneVIC3000, Australia
| | - Xiao Ma
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Faculty of Pharmacy and Pharmaceutical Sciences, Monash University, ParkvilleVIC3052, Australia
- Department of Systems Biology, Laboratory of Systems Pharmacology, Harvard Medical School, Boston, MA02115
| | - Simon J. Hogg
- Cancer Biology Therapeutics Program, Peter MacCallum Cancer Centre, MelbourneVIC3000, Australia
- Oncology Discovery Research, Abbvie, South San Francisco, CA94080
| | - Jackson He
- Blood Cancer Therapeutics Laboratory, School of Clinical Sciences at Monash Health, Faculty of Medicine Nursing and Health Sciences, Monash University, MelbourneVIC3168, Australia
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Faculty of Pharmacy and Pharmaceutical Sciences, Monash University, ParkvilleVIC3052, Australia
| | - Conor Kearney
- Olivia Newton-John Cancer Research Institute, HeidelbergVIC3084, Australia
- School of Cancer Medicine, La Trobe University, HeidelbergVIC3084, Australia
| | - Daniella Brasacchio
- Blood Cancer Therapeutics Laboratory, School of Clinical Sciences at Monash Health, Faculty of Medicine Nursing and Health Sciences, Monash University, MelbourneVIC3168, Australia
| | - Olivia Susanto
- Blood Cancer Therapeutics Laboratory, School of Clinical Sciences at Monash Health, Faculty of Medicine Nursing and Health Sciences, Monash University, MelbourneVIC3168, Australia
| | - Belinda Maher
- Blood Cancer Therapeutics Laboratory, School of Clinical Sciences at Monash Health, Faculty of Medicine Nursing and Health Sciences, Monash University, MelbourneVIC3168, Australia
| | - Ian G. Jennings
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Faculty of Pharmacy and Pharmaceutical Sciences, Monash University, ParkvilleVIC3052, Australia
| | - Andrea Newbold
- Cancer Biology Therapeutics Program, Peter MacCallum Cancer Centre, MelbourneVIC3000, Australia
- Sir Peter MacCallum Department of Medical Oncology, University of Melbourne, MelbourneVIC3000, Australia
| | - Peter Fraser
- Cancer Biology Therapeutics Program, Peter MacCallum Cancer Centre, MelbourneVIC3000, Australia
- Sir Peter MacCallum Department of Medical Oncology, University of Melbourne, MelbourneVIC3000, Australia
| | - Emily Gruber
- Cancer Biology Therapeutics Program, Peter MacCallum Cancer Centre, MelbourneVIC3000, Australia
- Sir Peter MacCallum Department of Medical Oncology, University of Melbourne, MelbourneVIC3000, Australia
| | - Lev M. Kats
- Cancer Biology Therapeutics Program, Peter MacCallum Cancer Centre, MelbourneVIC3000, Australia
- Sir Peter MacCallum Department of Medical Oncology, University of Melbourne, MelbourneVIC3000, Australia
| | - Gareth P. Gregory
- Blood Cancer Therapeutics Laboratory, School of Clinical Sciences at Monash Health, Faculty of Medicine Nursing and Health Sciences, Monash University, MelbourneVIC3168, Australia
- Monash Haematology, Monash Health, MelbourneVIC3168, Australia
- Cancer Biology Therapeutics Program, Peter MacCallum Cancer Centre, MelbourneVIC3000, Australia
| | - Ricky W. Johnstone
- Cancer Biology Therapeutics Program, Peter MacCallum Cancer Centre, MelbourneVIC3000, Australia
- Sir Peter MacCallum Department of Medical Oncology, University of Melbourne, MelbourneVIC3000, Australia
| | - Philip E. Thompson
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Faculty of Pharmacy and Pharmaceutical Sciences, Monash University, ParkvilleVIC3052, Australia
| | - Jake Shortt
- Blood Cancer Therapeutics Laboratory, School of Clinical Sciences at Monash Health, Faculty of Medicine Nursing and Health Sciences, Monash University, MelbourneVIC3168, Australia
- Monash Haematology, Monash Health, MelbourneVIC3168, Australia
- Cancer Biology Therapeutics Program, Peter MacCallum Cancer Centre, MelbourneVIC3000, Australia
- Sir Peter MacCallum Department of Medical Oncology, University of Melbourne, MelbourneVIC3000, Australia
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3
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Mohammed EUR, Porter ZJ, Jennings IG, Al-Rawi JMA, Thompson PE, Angove MJ. Synthesis and biological evaluation of 4H-benzo[e][1,3]oxazin-4-ones analogues of TGX-221 as inhibitors of PI3Kβ. Bioorg Med Chem 2022; 69:116832. [PMID: 35752141 DOI: 10.1016/j.bmc.2022.116832] [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: 02/10/2022] [Revised: 05/10/2022] [Accepted: 05/12/2022] [Indexed: 11/25/2022]
Abstract
A novel series of TGX-221 analogues was prepared that include isosteric replacement of the 4H-pyrido[1,2-a]pyrimidin-4-one with a 4H-benzo[e][1,3]oxazin-4-one scaffold. The compounds that included an CH(CH3)NH type linker showed comparable activity to TGX-221 analogues with the isosterism supported by the comparative SAR analysis. The analogues containing an CH(CH3)O linker were less active but still showed useful SAR including a favoured o-methyl substitution.
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Affiliation(s)
- Ehtesham U R Mohammed
- Pharmacy and Biomedical Sciences, La Trobe Institute for Molecular Science, La Trobe University, P.O. Box 199, Bendigo, VIC 3552, Australia.
| | - Zoe J Porter
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, VIC 3052, Australia
| | - Ian G Jennings
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, VIC 3052, Australia
| | - Jasim M A Al-Rawi
- Pharmacy and Biomedical Sciences, La Trobe Institute for Molecular Science, La Trobe University, P.O. Box 199, Bendigo, VIC 3552, Australia
| | - Philip E Thompson
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, VIC 3052, Australia
| | - Michael J Angove
- Pharmacy and Biomedical Sciences, La Trobe Institute for Molecular Science, La Trobe University, P.O. Box 199, Bendigo, VIC 3552, Australia
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4
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Selvadurai MV, Moon MJ, Mountford SJ, Ma X, Zheng Z, Jennings IG, Setiabakti NM, Iman RP, Brazilek RJ, Z Abidin NA, Chicanne G, Severin S, Nicholls AJ, Wong CHY, Rinckel JY, Eckly A, Gachet C, Nesbitt WS, Thompson PE, Hamilton JR. Disrupting the platelet internal membrane via PI3KC2α inhibition impairs thrombosis independently of canonical platelet activation. Sci Transl Med 2021; 12:12/553/eaar8430. [PMID: 32718993 DOI: 10.1126/scitranslmed.aar8430] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 03/12/2020] [Accepted: 06/05/2020] [Indexed: 12/17/2022]
Abstract
Arterial thrombosis causes heart attacks and most strokes and is the most common cause of death in the world. Platelets are the cells that form arterial thrombi, and antiplatelet drugs are the mainstay of heart attack and stroke prevention. Yet, current drugs have limited efficacy, preventing fewer than 25% of lethal cardiovascular events without clinically relevant effects on bleeding. The key limitation on the ability of all current drugs to impair thrombosis without causing bleeding is that they block global platelet activation, thereby indiscriminately preventing platelet function in hemostasis and thrombosis. Here, we identify an approach with the potential to overcome this limitation by preventing platelet function independently of canonical platelet activation and in a manner that appears specifically relevant in the setting of thrombosis. Genetic or pharmacological targeting of the class II phosphoinositide 3-kinase (PI3KC2α) dilates the internal membrane reserve of platelets but does not affect activation-dependent platelet function in standard tests. Despite this, inhibition of PI3KC2α is potently antithrombotic in human blood ex vivo and mice in vivo and does not affect hemostasis. Mechanistic studies reveal this antithrombotic effect to be the result of impaired platelet adhesion driven by pronounced hemodynamic shear stress gradients. These findings demonstrate an important role for PI3KC2α in regulating platelet structure and function via a membrane-dependent mechanism and suggest that drugs targeting the platelet internal membrane may be a suitable approach for antithrombotic therapies with an improved therapeutic window.
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Affiliation(s)
- Maria V Selvadurai
- Australian Centre for Blood Diseases, Monash University, Melbourne, VIC 3004, Australia
| | - Mitchell J Moon
- Australian Centre for Blood Diseases, Monash University, Melbourne, VIC 3004, Australia
| | - Simon J Mountford
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
| | - Xiao Ma
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
| | - Zhaohua Zheng
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
| | - Ian G Jennings
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
| | - Natasha M Setiabakti
- Australian Centre for Blood Diseases, Monash University, Melbourne, VIC 3004, Australia.,Faculty of Medicine, Universitas Indonesia, Salemba, Jakarta 10430, Indonesia
| | - Rizani P Iman
- Australian Centre for Blood Diseases, Monash University, Melbourne, VIC 3004, Australia.,Faculty of Medicine, Universitas Indonesia, Salemba, Jakarta 10430, Indonesia
| | - Rose J Brazilek
- Australian Centre for Blood Diseases, Monash University, Melbourne, VIC 3004, Australia
| | - Nurul Aisha Z Abidin
- Australian Centre for Blood Diseases, Monash University, Melbourne, VIC 3004, Australia
| | - Gaëtan Chicanne
- Institut des Maladies Métaboliques et Cardiovasculaires, Inserm U1048, Université Toulouse III, 31432 Toulouse CEDEX 4, France
| | - Sonia Severin
- Institut des Maladies Métaboliques et Cardiovasculaires, Inserm U1048, Université Toulouse III, 31432 Toulouse CEDEX 4, France
| | - Alyce J Nicholls
- Centre for Inflammatory Diseases, Department of Medicine, Monash Medical Centre, Monash University, Clayton, VIC 3800, Australia
| | - Connie H Y Wong
- Centre for Inflammatory Diseases, Department of Medicine, Monash Medical Centre, Monash University, Clayton, VIC 3800, Australia
| | - Jean-Yves Rinckel
- Université de Strasbourg, INSERM, EFS Grand Est, BPPS UMR-S 1255, FMTS, F-67000 Strasbourg, France
| | - Anita Eckly
- Université de Strasbourg, INSERM, EFS Grand Est, BPPS UMR-S 1255, FMTS, F-67000 Strasbourg, France
| | - Christian Gachet
- Université de Strasbourg, INSERM, EFS Grand Est, BPPS UMR-S 1255, FMTS, F-67000 Strasbourg, France
| | - Warwick S Nesbitt
- Australian Centre for Blood Diseases, Monash University, Melbourne, VIC 3004, Australia.,Microplatforms Research Group, School of Engineering, RMIT University, Melbourne, VIC 3000, Australia
| | - Philip E Thompson
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
| | - Justin R Hamilton
- Australian Centre for Blood Diseases, Monash University, Melbourne, VIC 3004, Australia.
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5
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Morrison R, Zheng Z, Jennings IG, Thompson PE, Al-Rawi JMA. Synthesis of linear and angular aryl-morpholino-naphth-oxazines, their DNA-PK, PI3K, PDE3A and antiplatelet activity. Bioorg Med Chem Lett 2016; 26:5534-5538. [PMID: 27765510 DOI: 10.1016/j.bmcl.2016.10.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Revised: 10/01/2016] [Accepted: 10/04/2016] [Indexed: 10/20/2022]
Abstract
To continue our study of 2-morpholino-benzoxazine based compounds, which show useful activity against PI3K family enzymes or antiplatelet activity, we designed and synthesized a series of linear 6.7-fused, 5,6-angular fused and 7,8-angular fused-aryl-morpholino-naphth-oxazines. The compounds were prepared from substituted 2-hydroxynaphthoic acid to give the corresponding thioxo analogues 8, 9, 15 and 19. The thioxo products were then converted to the morpholino substituted analogue. The aryl group was introduced by Suzuki coupling of bromo precursors. The products were evaluated for activity at PI3K family enzymes and as platelet aggregation inhibitors and compared to reported unsubstituted analogues. The linear 6.7-fused product 13a and 13b were moderated potent but selective PI3Kδ isoform inhibitors (IC50=7.7 and 5.61μM). Good antiplatelet activity was noticed for the angular 7,8-fused compounds 22a, b, k and l with IC50=3.0,14.0, 2.0 and 5.0μM respectively. The antiplatelet activity is independent of PDE3.
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Affiliation(s)
- Rick Morrison
- Pharmacy and Applied Science, La Trobe Institute for Molecular Science, La Trobe University, PO Box 199, Bendigo, VIC 3552, Australia.
| | - Zhaohua Zheng
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, VIC 3052, Australia.
| | - Ian G Jennings
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, VIC 3052, Australia.
| | - Philip E Thompson
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, VIC 3052, Australia.
| | - Jasim M A Al-Rawi
- Pharmacy and Applied Science, La Trobe Institute for Molecular Science, La Trobe University, PO Box 199, Bendigo, VIC 3552, Australia.
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6
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Zheng Z, Pinson JA, Mountford SJ, Orive S, Schoenwaelder SM, Shackleford D, Powell A, Nelson EM, Hamilton JR, Jackson SP, Jennings IG, Thompson PE. Discovery and antiplatelet activity of a selective PI3Kβ inhibitor (MIPS-9922). Eur J Med Chem 2016; 122:339-351. [PMID: 27387421 DOI: 10.1016/j.ejmech.2016.06.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Revised: 06/06/2016] [Accepted: 06/08/2016] [Indexed: 01/08/2023]
Abstract
A series of amino-substituted triazines were developed and examined for PI3Kβ inhibition and anti-platelet function. Structural adaptations of a morpholine ring of the prototype pan-PI3K inhibitor ZSTK474 yielded PI3Kβ selective compounds, where the selectivity largely derives from an interaction with the non-conserved Asp862 residue, as shown by site directed mutagenesis. The most PI3Kβ selective inhibitor from the series was studied in detail through a series of in vitro and in vivo functional studies. MIPS-9922, 10 potently inhibited ADP-induced washed platelet aggregation. It also inhibited integrin αIIbβ3 activation and αIIbβ3 dependent platelet adhesion to immobilized vWF under high shear. It prevented arterial thrombus formation in the in vivo electrolytic mouse model of thrombosis without inducing prolonged bleeding or excess blood loss.
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Affiliation(s)
- Zhaohua Zheng
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia; Australian Centre for Blood Diseases, Monash University, Alfred Medical Research and Education Precinct (AMREP), 89 Commercial Road, Prahran, Victoria 3004, Australia
| | - Jo-Anne Pinson
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | - Simon J Mountford
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | - Stephanie Orive
- Australian Centre for Blood Diseases, Monash University, Alfred Medical Research and Education Precinct (AMREP), 89 Commercial Road, Prahran, Victoria 3004, Australia
| | - Simone M Schoenwaelder
- Australian Centre for Blood Diseases, Monash University, Alfred Medical Research and Education Precinct (AMREP), 89 Commercial Road, Prahran, Victoria 3004, Australia
| | - David Shackleford
- Centre for Drug Candidate Optimisation, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | - Andrew Powell
- Centre for Drug Candidate Optimisation, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | - Erin M Nelson
- Australian Centre for Blood Diseases, Monash University, Alfred Medical Research and Education Precinct (AMREP), 89 Commercial Road, Prahran, Victoria 3004, Australia
| | - Justin R Hamilton
- Australian Centre for Blood Diseases, Monash University, Alfred Medical Research and Education Precinct (AMREP), 89 Commercial Road, Prahran, Victoria 3004, Australia
| | - Shaun P Jackson
- Australian Centre for Blood Diseases, Monash University, Alfred Medical Research and Education Precinct (AMREP), 89 Commercial Road, Prahran, Victoria 3004, Australia
| | - Ian G Jennings
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | - Philip E Thompson
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia.
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7
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Howard BL, Harvey KL, Stewart RJ, Azevedo MF, Crabb BS, Jennings IG, Sanders PR, Manallack DT, Thompson PE, Tonkin CJ, Gilson PR. Identification of potent phosphodiesterase inhibitors that demonstrate cyclic nucleotide-dependent functions in apicomplexan parasites. ACS Chem Biol 2015; 10:1145-54. [PMID: 25555060 DOI: 10.1021/cb501004q] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Apicomplexan parasites, including Plasmodium falciparum and Toxoplasma gondii, the causative agents of severe malaria and toxoplasmosis, respectively, undergo several critical developmental transitions during their lifecycle. Most important for human pathogenesis is the asexual cycle, in which parasites undergo rounds of host cell invasion, replication, and egress (exit), destroying host cell tissue in the process. Previous work has identified important roles for Protein Kinase G (PKG) and Protein Kinase A (PKA) in parasite egress and invasion, yet little is understood about the regulation of cyclic nucleotides, cGMP and cAMP, that activate these enzymes. To address this, we have focused upon the development of inhibitors of 3',5'-cyclic nucleotide phosphodiesterases (PDEs) to block the breakdown of cyclic nucleotides. This was done by repurposing human PDE inhibitors noting various similarities of the human and apicomplexan PDE binding sites. The most potent inhibitors blocked the in vitro proliferation of P. falciparum and T. gondii more potently than the benchmark compound zaprinast. 5-Benzyl-3-isopropyl-1H-pyrazolo[4,3-d]pyrimidin-7(6H)-one (BIPPO) was found to be a potent inhibitor of recombinant P. falciparum PfPDEα and activated PKG-dependent egress of T. gondii and P. falciparum, likely by promoting the exocytosis of micronemes, an activity that was reversed by a specific Protein Kinase G inhibitor. BIPPO also promotes cAMP-dependent phosphorylation of a P. falciparum ligand critical for host cell invasion, suggesting that the compound inhibits single or multiple PDE isoforms that regulate both cGMP and cAMP levels. BIPPO is therefore a useful tool for the dissection of signal transduction pathways in apicomplexan parasites.
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Affiliation(s)
- Brittany L. Howard
- Monash
Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
| | - Katherine L. Harvey
- Macfarlane Burnet Institute, Melbourne, Victoria, Australia
- University of Melbourne, Melbourne, Victoria, Australia
| | - Rebecca J. Stewart
- The Walter & Eliza Hall Institute, Melbourne, Victoria, Australia
- Department
of Medical Biology, The University of Melbourne, Parkville, Victoria 3010, Australia
| | | | - Brendan S. Crabb
- Monash
Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
- Macfarlane Burnet Institute, Melbourne, Victoria, Australia
- University of Melbourne, Melbourne, Victoria, Australia
| | - Ian G. Jennings
- Monash
Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
| | | | - David T. Manallack
- Monash
Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
| | - Philip E. Thompson
- Monash
Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
| | - Christopher J. Tonkin
- The Walter & Eliza Hall Institute, Melbourne, Victoria, Australia
- Department
of Medical Biology, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Paul R. Gilson
- Monash
Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
- Macfarlane Burnet Institute, Melbourne, Victoria, Australia
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8
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Mountford SJ, Zheng Z, Sundaram K, Jennings IG, Hamilton JR, Thompson PE. Class II but Not Second Class-Prospects for the Development of Class II PI3K Inhibitors. ACS Med Chem Lett 2015; 6:3-6. [PMID: 25589915 DOI: 10.1021/ml500354e] [Citation(s) in RCA: 7] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The Class II PI3 kinases are emerging from the shadows of their Class I cousins. The data emerging from PIK3C2 genetic modification studies and from siRNA knockdown suggest important roles in physiology and pathology. With some well-studied Class I isoform inhibitors showing strong Class II activity and a wealth of crystallographic information available, the structural similarity of these isoforms to Class I provides both the opportunity and the challenge in design of selective pharmacological inhibitors.
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Affiliation(s)
- Simon J. Mountford
- Medicinal
Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University (Parkville Campus), 381 Royal Parade, Parkville, Victoria 3052, Australia
| | - Zhaohua Zheng
- Medicinal
Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University (Parkville Campus), 381 Royal Parade, Parkville, Victoria 3052, Australia
- Australian
Centre for Blood Diseases and Department of Clinical Haematology,
L6, Monash University, 89 Commerical Road, Prahran, Victoria 3181, Australia
| | - Krithika Sundaram
- Medicinal
Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University (Parkville Campus), 381 Royal Parade, Parkville, Victoria 3052, Australia
| | - Ian G. Jennings
- Medicinal
Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University (Parkville Campus), 381 Royal Parade, Parkville, Victoria 3052, Australia
| | - Justin R. Hamilton
- Australian
Centre for Blood Diseases and Department of Clinical Haematology,
L6, Monash University, 89 Commerical Road, Prahran, Victoria 3181, Australia
| | - Philip E. Thompson
- Medicinal
Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University (Parkville Campus), 381 Royal Parade, Parkville, Victoria 3052, Australia
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9
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Miller MS, Schmidt-Kittler O, Bolduc DM, Brower ET, Chaves-Moreira D, Allaire M, Kinzler KW, Jennings IG, Thompson PE, Cole PA, Amzel LM, Vogelstein B, Gabelli SB. Abstract LB-326: Structural basis of lipid-binding and regulation in PI3Kα. Cancer Res 2014. [DOI: 10.1158/1538-7445.am2014-lb-326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
PI3Kα is a well-established target for the development of novel cancer therapeutics. Currently, all inhibitors in clinical trials target the highly conserved ATP-binding site, which has made the development of PI3K selective inhibitors difficult, with many inhibitors displaying cross-reactivity against protein kinases.
We have used X-ray crystallography and fluorescence quenching studies to characterize the lipid-binding site of PI3Kα and the structural basis of regulation by nSH2. A newly determined p110α/niSH2 crystal structure is the first to reveal the nSH2 domain in complex with wild-type p110α, allowing investigation of the mechanisms of nSH2 regulation. Key interactions between the nSH2 domain and the activation loop suggest a mechanism by which the kinase domain is kept in an inactive conformation until activation by phosphopeptide binding. Key differences in nSH2 domain binding to p110α were identified between the wild-type and oncogenic mutant, p110αH1047R. Increased buried surface area and two unique salt-bridges are suggestive of tighter regulatory control in the wild-type PI3Kα compared with the oncogenic mutant. A second structure reveals the details of PI3K binding to a lipid substrate mimetic, diC4-PIP2. Unexpectedly, we found an additional lipid-binding site, and this striking observation was confirmed by fluorescence quenching experiments. The identification of multiple lipid binding sites provides additional targets that may enable more selective inhibition among the various isoforms, or even between mutant and wild-type forms of PI3Kα.
Citation Format: Michelle S. Miller, Oleg Schmidt-Kittler, David M. Bolduc, Evan T. Brower, Daniele Chaves-Moreira, Marc Allaire, Kenneth W. Kinzler, Ian G. Jennings, Philip E. Thompson, Philip A. Cole, L. Mario Amzel, Bert Vogelstein, Sandra B. Gabelli. Structural basis of lipid-binding and regulation in PI3Kα. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-326. doi:10.1158/1538-7445.AM2014-LB-326
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Affiliation(s)
| | | | | | - Evan T. Brower
- 1Johns Hopkins University School of Medicine, Baltimore, MD
| | | | | | | | - Ian G. Jennings
- 4Monash Institute of Pharmaceutical Sciences, Melbourne, Australia
| | | | - Philip A. Cole
- 1Johns Hopkins University School of Medicine, Baltimore, MD
| | - L. Mario Amzel
- 1Johns Hopkins University School of Medicine, Baltimore, MD
| | - Bert Vogelstein
- 3Ludwig Center for Cancer Genetics and Therapeutics, Baltimore, MD
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10
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Abstract
The p110β isoform of PI3 kinase (PI3Kβ) has been implicated in pathological disorders such as thrombosis and cancer and a number of PI3Kβ-selective inhibitors have recently progressed into clinical studies. Although crystallography studies identify a binding site conformation favored by the inhibitors, no specific interaction explains the observed selectivity. Using site-directed mutagenesis we have identified a specific tyrosine residue of the binding site Y778 that dictates the ability of the PI3Kβ isoform to bind these inhibitors. When mutated to isoleucine, PI3Kβ has reduced ability to present a specific cryptic binding site into which a range of reported PI3Kβ inhibitors can bind, and conversely when tyrosine is introduced into the same position in PI3Kα, the same inhibitors gain potency. The results provide a cogent explanation for the selectivity profiles displayed by these PI3K inhibitors and maybe others as well.
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Affiliation(s)
- Zhaohua Zheng
- Medicinal Chemistry, Monash Institute of Pharmaceutical
Sciences, Monash University, 381 Royal
Parade, Parkville 3052, Australia
| | - Michelle S. Miller
- Medicinal Chemistry, Monash Institute of Pharmaceutical
Sciences, Monash University, 381 Royal
Parade, Parkville 3052, Australia
| | - Ian G. Jennings
- Medicinal Chemistry, Monash Institute of Pharmaceutical
Sciences, Monash University, 381 Royal
Parade, Parkville 3052, Australia
| | - Philip E. Thompson
- Medicinal Chemistry, Monash Institute of Pharmaceutical
Sciences, Monash University, 381 Royal
Parade, Parkville 3052, Australia
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11
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O'Brien NJ, Amran S, Medan J, Cleary B, Deady LW, Jennings IG, Thompson PE, Abbott BM. Potent inhibitors of phosphatidylinositol 3 (PI3) kinase that have antiproliferative activity only when delivered as prodrug forms. ChemMedChem 2013; 8:914-8. [PMID: 23568455 DOI: 10.1002/cmdc.201200583] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Indexed: 11/07/2022]
Abstract
Prodrugs for PI3K: A series of substituted analogues of the phosphatidylinositol 3 kinase (PI3K) inhibitor LY294002 were prepared and found to potently inhibit the isolated enzyme but not MCF7 cell proliferation. Two tetrazolyl-substituted analogues were further derivatized as prodrugs resulting in restoration of cell-based activity. These data provide a conceptual model for development of tumor-targeting prodrug forms of cell-impermeable PI3K inhibitors.
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Affiliation(s)
- Nathan J O'Brien
- Department of Chemistry, La Trobe University Institute for Molecular Science, La Trobe University, Bundoora, Victoria 3086, Australia
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12
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Pinson JA, Zheng Z, Miller MS, Chalmers DK, Jennings IG, Thompson PE. L-Aminoacyl-triazine derivatives are isoform-selective PI3Kβ inhibitors that target non-conserved Asp862 of PI3Kβ. ACS Med Chem Lett 2013; 4:206-210. [PMID: 23795239 DOI: 10.1021/ml300336j] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [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: 12/26/2022] Open
Abstract
A series of aminoacyl-triazine derivatives based upon the pan-PI3K inhibitor ZSTK474 were identified as potent and isoform selective inhibitors of PI3Kβ. The compounds showed selectivity based upon stereochemistry with L-amino acyl derivatives preferring PI3Kβ while their D-congeners favoured PI3Kδ. The mechanistic basis of this inhibition was studied using site-directed mutants. One Asp residue, D862 was identified as a critical participant in binding to the PI3Kβ-selective inhibitors distinguishing this class from other reported PI3Kβ-selective inhibitors. The compounds show strong inhibition of cellular Akt phosphorylation and growth of PTEN-deficient MD-MBA-468 cells.
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Affiliation(s)
- Jo-Anne Pinson
- Medicinal Chemistry, Monash
Institute of Pharmaceutical Sciences, Monash University, 381 Royal
Parade, Parkville 3052 Australia
| | - Zhaohua Zheng
- Medicinal Chemistry, Monash
Institute of Pharmaceutical Sciences, Monash University, 381 Royal
Parade, Parkville 3052 Australia
| | - Michelle S. Miller
- Medicinal Chemistry, Monash
Institute of Pharmaceutical Sciences, Monash University, 381 Royal
Parade, Parkville 3052 Australia
| | - David K. Chalmers
- Medicinal Chemistry, Monash
Institute of Pharmaceutical Sciences, Monash University, 381 Royal
Parade, Parkville 3052 Australia
| | - Ian G. Jennings
- Medicinal Chemistry, Monash
Institute of Pharmaceutical Sciences, Monash University, 381 Royal
Parade, Parkville 3052 Australia
| | - Philip E. Thompson
- Medicinal Chemistry, Monash
Institute of Pharmaceutical Sciences, Monash University, 381 Royal
Parade, Parkville 3052 Australia
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13
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Miller MS, Pinson JA, Zheng Z, Jennings IG, Thompson PE. Regioselective synthesis of 5- and 6-methoxybenzimidazole-1,3,5-triazines as inhibitors of phosphoinositide 3-kinase. Bioorg Med Chem Lett 2013; 23:802-5. [DOI: 10.1016/j.bmcl.2012.11.076] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2012] [Revised: 11/19/2012] [Accepted: 11/20/2012] [Indexed: 10/27/2022]
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14
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Pinson JA, Schmidt-Kittler O, Frazzetto M, Zheng Z, Jennings IG, Kinzler KW, Vogelstein B, Chalmers DK, Thompson PE. Synthesis and Pharmacological Evaluation of 4-Iminothiazolidinones for Inhibition of PI3 Kinase. Aust J Chem 2012; 65:1396-1404. [PMID: 23997244 DOI: 10.1071/ch12140] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The thiazolidinedione, compound 1, has previously shown pan-inhibition of the phosphoinositide 3-kinase (PI3K) class I isoforms. We hypothesized the derivatization of the thiazolidinedione core of compound 1 could introduce isoform selectivity. We report the synthesis, characterization, and inhibitory activity of a novel series of 4-iminothiazolidin-2-ones for inhibition of the class I PI3K isoforms. Their synthesis was successfully achieved by multiple pathways described in this paper. Initial in vitro data of 28 analogues demonstrated poor inhibition of all class I PI3K isoforms. However, we identified an alternate target, the phosphodiesterases, and present preliminary screening results showing improved inhibitory activity.
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Affiliation(s)
- Jo-Anne Pinson
- Department of Medicinal Chemistry, Faculty of Pharmacy and Pharmaceutical Sciences, Monash Institute of Pharmaceutical Sciences, Monash University (Parkville Campus), Parkville, Vic. 3052, Australia
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15
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Nankervis JL, Feil SC, Hancock NC, Zheng Z, Ng HL, Morton CJ, Holien JK, Ho PW, Frazzetto MM, Jennings IG, Manallack DT, John Martin T, Thompson PE, Parker MW. Thiophene inhibitors of PDE4: Crystal structures show a second binding mode at the catalytic domain of PDE4D2. Bioorg Med Chem Lett 2011; 21:7089-93. [DOI: 10.1016/j.bmcl.2011.09.109] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Revised: 09/21/2011] [Accepted: 09/21/2011] [Indexed: 12/21/2022]
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16
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Zheng Z, Amran SI, Thompson PE, Jennings IG. Isoform-selective inhibition of phosphoinositide 3-kinase: identification of a new region of nonconserved amino acids critical for p110α inhibition. Mol Pharmacol 2011; 80:657-64. [PMID: 21778304 DOI: 10.1124/mol.111.072546] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The combination of molecular modeling and X-ray crystallography has failed to yield a consensus model of the mechanism for selective binding of inhibitors to the phosphoinositide 3-kinase (PI3K) p110 α-isoform. Here we have used kinetic analysis to determine that the p110α-selective inhibitor 2-methyl-5-nitro-2-[(6-bromoimidazo[1,2-α]pyridin-3-yl)methylene]-1-methylhydrazide-benzenesulfonic acid (PIK-75) is a competitive inhibitor with respect to a substrate, phosphatidylinositol (PI) in contrast to most other PI3K inhibitors, which bind at or near the ATP site. Using sequence analysis and the existing crystal structures of inhibitor complexes with the p110γ and -δ isoforms, we have identified a new region of nonconserved amino acids (region 2) that was postulated to be involved in PIK-75 p110α selectivity. Analysis of region 2, using in vitro mutation of identified nonconserved amino acids to alanine, showed that Ser773 was a critical amino acid involved in PIK-75 binding, with an 8-fold-increase in the IC(50) compared with wild-type. Kinetic analysis showed that, with respect to PI, the PIK-75 K(i) for the isoform mutant S773D increased 64-fold compared with wild-type enzyme. In addition, a nonconserved amino acid, His855, from the previously identified region 1 of nonconserved amino acids, was found to be involved in PIK-75 binding. These results show that these two regions of nonconserved amino acids that are close to the substrate binding site could be targeted to produce p110α isoform-selective inhibitors.
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Affiliation(s)
- Zhaohua Zheng
- Medicinal Chemistry & Drug Action, Monash Institute of Pharmaceutical Sciences, Monash University (Parkville Campus),Victoria, Australia
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17
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Pinson JA, Schmidt-Kittler O, Zhu J, Jennings IG, Kinzler KW, Vogelstein B, Chalmers DK, Thompson PE. Thiazolidinedione-based PI3Kα inhibitors: an analysis of biochemical and virtual screening methods. ChemMedChem 2011; 6:514-22. [PMID: 21360822 PMCID: PMC3187668 DOI: 10.1002/cmdc.201000467] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2010] [Revised: 11/29/2010] [Indexed: 12/27/2022]
Abstract
A series of synthesized and commercially available compounds were assessed against PI3Kα for in vitro inhibitory activity and the results compared to binding calculated in silico. Using published crystal structures of PI3Kγ and PI3Kδ co-crystallized with inhibitors as a template, docking was able to identify the majority of potent inhibitors from a decoy set of 1000 compounds. On the other hand, PI3Kα in the apo-form, modeled by induced fit docking, or built as a homology model gave only poor results. A PI3Kα homology model derived from a ligand-bound PI3Kδ crystal structure was developed that has a good ability to identify active compounds. The docking results identified binding poses for active compounds that differ from those identified to date and can contribute to our understanding of structure-activity relationships for PI3K inhibitors.
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Affiliation(s)
- Jo-Anne Pinson
- Medicinal Chemistry & Drug Action, Monash Institute of Pharmaceutical Sciences, Parkville, Victoria 3052, Australia
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18
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Frazzetto M, Suphioglu C, Zhu J, Schmidt-Kittler O, Jennings IG, Cranmer SL, Jackson SP, Kinzler KW, Vogelstein B, Thompson PE. Dissecting isoform selectivity of PI3K inhibitors: the role of non-conserved residues in the catalytic pocket. Biochem J 2008; 414:383-90. [PMID: 18489260 PMCID: PMC2820364 DOI: 10.1042/bj20080512] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The last few years have seen the identification of numerous small molecules that selectively inhibit specific class I isoforms of PI3K (phosphoinositide 3-kinase), yet little has been revealed about the molecular basis for the observed selectivities. Using site-directed mutagenesis, we have investigated one of the areas postulated as being critical to the observed selectivity. The residues Thr(886) and Lys(890) of the PI3Kgamma isoform project towards the ATP-binding pocket at the entrance to the catalytic site, but are not conserved. We have made reciprocal mutations between those residues in the beta isoform (Glu(858) and Asp(862)) and those in the alpha isoform (His(855) and Gln(859)) and evaluated the potency of a range of reported PI3K inhibitors. The results show that the potencies of beta-selective inhibitors TGX221 and TGX286 are unaffected by this change. In contrast, close analogues of these compounds, particularly the alpha-isoform-selective compound (III), are markedly influenced by the point mutations. The collected data suggests two distinct binding poses for these inhibitor classes, one of which is associated with potent PI3Kbeta activity and is not associated with the mutated residues, and a second that, in accord with earlier hypotheses, does involve this pair of non-conserved amino acids at the catalytic site entrance and contributes to the alpha-isoform-selectivity of the compounds studied.
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Affiliation(s)
- Mark Frazzetto
- Australian Centre for Blood Diseases, Monash University, Melbourne, VIC, Australia
| | - Cenk Suphioglu
- Australian Centre for Blood Diseases, Monash University, Melbourne, VIC, Australia
| | - Jiuxiang Zhu
- Johns Hopkins University, Sidney Kimmel Cancer Centre, Baltimore, USA
| | | | - Ian G. Jennings
- Victorian College of Pharmacy, Monash University, Parkville, VIC, Australia
| | - Susan. L. Cranmer
- Australian Centre for Blood Diseases, Monash University, Melbourne, VIC, Australia
| | - Shaun P. Jackson
- Australian Centre for Blood Diseases, Monash University, Melbourne, VIC, Australia
| | | | - Bert Vogelstein
- Johns Hopkins University, Sidney Kimmel Cancer Centre, Baltimore, USA
| | - Philip E. Thompson
- Victorian College of Pharmacy, Monash University, Parkville, VIC, Australia
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19
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Fulton D, Church JE, Ruan L, Li C, Sood SG, Kemp BE, Jennings IG, Venema RC. Src Kinase Activates Endothelial Nitric-oxide Synthase by Phosphorylating Tyr-83. J Biol Chem 2005; 280:35943-52. [PMID: 16123043 DOI: 10.1074/jbc.m504606200] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [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
The endothelial nitric-oxide synthase (eNOS) is regulated in part by serine/threonine phosphorylation, but eNOS tyrosine phosphorylation is less well understood. In the present study we have examined the tyrosine phosphorylation of eNOS in bovine aortic endothelial cells (BAECs) exposed to oxidant stress. Hydrogen peroxide and pervanadate (PV) treatment stimulates eNOS tyrosine phosphorylation in BAECs. Phosphorylation is blocked by the Src kinase family inhibitor, 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2). Moreover, eNOS and c-Src can be coimmunoprecipitated from BAEC lysates by antibodies directed against either protein. Domain mapping and site-directed mutagenesis studies in COS-7 cells transfected with either eNOS alone and then treated with PV or cotransfected with eNOS and constitutively active v-Src identified Tyr-83 (bovine sequence) as the major eNOS tyrosine phosphorylation site. Tyr-83 phosphorylation is associated with a 3-fold increase in basal NO release from cotransfected cells. Furthermore, the Y83F eNOS mutation attenuated thapsigargin-stimulated NO production. Taken together, these data indicate that Src-mediated tyrosine phosphorylation of eNOS at Tyr-83 modulates eNOS activity in endothelial cells.
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Affiliation(s)
- David Fulton
- Vascular Biology Center and Department of Pediatrics, Medical College of Georgia, Augusta, Georgia 30912-2500, USA
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20
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Polekhina G, Gupta A, Michell BJ, van Denderen B, Murthy S, Feil SC, Jennings IG, Campbell DJ, Witters LA, Parker MW, Kemp BE, Stapleton D. AMPK beta subunit targets metabolic stress sensing to glycogen. Curr Biol 2003; 13:867-71. [PMID: 12747837 DOI: 10.1016/s0960-9822(03)00292-6] [Citation(s) in RCA: 336] [Impact Index Per Article: 16.0] [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: 11/18/2022]
Abstract
AMP-activated protein kinase (AMPK) is a multisubstrate enzyme activated by increases in AMP during metabolic stress caused by exercise, hypoxia, lack of cell nutrients, as well as hormones, including adiponectin and leptin. Furthermore, metformin and rosiglitazone, frontline drugs used for the treatment of type II diabetes, activate AMPK. Mammalian AMPK is an alphabetagamma heterotrimer with multiple isoforms of each subunit comprising alpha1, alpha2, beta1, beta2, gamma1, gamma2, and gamma3, which have varying tissue and subcellular expression. Mutations in the AMPK gamma subunit cause glycogen storage disease in humans, but the molecular relationship between glycogen and the AMPK/Snf1p kinase subfamily has not been apparent. We show that the AMPK beta subunit contains a functional glycogen binding domain (beta-GBD) that is most closely related to isoamylase domains found in glycogen and starch branching enzymes. Mutation of key glycogen binding residues, predicted by molecular modeling, completely abolished beta-GBD binding to glycogen. AMPK binds to glycogen but retains full activity. Overexpressed AMPK beta1 localized to specific mammalian subcellular structures that corresponded with the expression pattern of glycogen phosphorylase. Glycogen binding provides an architectural link between AMPK and a major cellular energy store and juxtaposes AMPK to glycogen bound phosphatases.
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Affiliation(s)
- Galina Polekhina
- St. Vincent's Institute of Medical Research, University of Melbourne, 41 Victoria Parade, Fitzroy, Australia
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21
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Kemp BE, Stapleton D, Campbell DJ, Chen ZP, Murthy S, Walter M, Gupta A, Adams JJ, Katsis F, van Denderen B, Jennings IG, Iseli T, Michell BJ, Witters LA. AMP-activated protein kinase, super metabolic regulator. Biochem Soc Trans 2003; 31:162-8. [PMID: 12546677 DOI: 10.1042/bst0310162] [Citation(s) in RCA: 383] [Impact Index Per Article: 18.2] [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: 11/17/2022]
Abstract
The AMP-activated protein kinase (AMPK) is a metabolic-stress-sensing protein kinase that regulates metabolism in response to energy demand and supply by directly phosphorylating rate-limiting enzymes in metabolic pathways as well as controlling gene expression.
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Affiliation(s)
- B E Kemp
- St. Vincent's Institute of Medical Research, and Department of Medicine, University of Melbourne, 41 Victoria Parade, Fitzroy, Vic. 3065, Australia.
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22
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Abstract
Phenylalanine hydroxylase (PAH) is activated by its substrate phenylalanine, and through phosphorylation by cAMP-dependent protein kinase at Ser16 in the N-terminal autoregulatory sequence of the enzyme. The crystal structures of phosphorylated and unphosphorylated forms of the enzyme showed that, in the absence of phenylalanine, in both cases the N-terminal 18 residues including the phosphorylation site contained no interpretable electron density. We used nuclear magnetic resonance (NMR) spectroscopy to characterize this N-terminal region of the molecule in different stages of the regulatory pathway. A number of sharp resonances are observed in PAH with an intact N-terminal region, but no sharp resonances are present in a truncation mutant lacking the N-terminal 29 residues. The N-terminal sequence therefore represents a mobile flexible region of the molecule. The resonances become weaker after the addition of phenylalanine, indicating a loss of mobility. The peptides corresponding to residues 2-20 of PAH have different structural characteristics in the phosphorylated and unphosphorylated forms, with the former showing increased secondary structure. Our results support the model whereby upon phenylalanine binding, the mobile N-terminal 18 residues of PAH associate with the folded core of the molecule; phosphorylation may facilitate this interaction.
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Affiliation(s)
- James Horne
- Structural Biology Laboratory, St. Vincent's Institute of Medical Research, Fitzroy, Victoria, 3065, Australia
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23
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Catimel B, Teh T, Fontes MR, Jennings IG, Jans DA, Howlett GJ, Nice EC, Kobe B. Biophysical characterization of interactions involving importin-alpha during nuclear import. J Biol Chem 2001; 276:34189-98. [PMID: 11448961 DOI: 10.1074/jbc.m103531200] [Citation(s) in RCA: 134] [Impact Index Per Article: 5.8] [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: 11/06/2022] Open
Abstract
Proteins containing the classical nuclear localization sequences (NLSs) are imported into the nucleus by the importin-alpha/beta heterodimer. Importin-alpha contains the NLS binding site, whereas importin-beta mediates the translocation through the nuclear pore. We characterized the interactions involving importin-alpha during nuclear import using a combination of biophysical techniques (biosensor, crystallography, sedimentation equilibrium, electrophoresis, and circular dichroism). Importin-alpha is shown to exist in a monomeric autoinhibited state (association with NLSs undetectable by biosensor). Association with importin-beta (stoichiometry, 1:1; K(D) = 1.1 x 10(-8) m) increases the affinity for NLSs; the importin-alpha/beta complex binds representative monopartite NLS (simian virus 40 large T-antigen) and bipartite NLS (nucleoplasmin) with affinities (K(D) = 3.5 x 10(-8) m and 4.8 x 10(-8) m, respectively) comparable with those of a truncated importin-alpha lacking the autoinhibitory domain (T-antigen NLS, K(D) = 1.7 x 10(-8) m; nucleoplasmin NLS, K(D) = 1.4 x 10(-8) m). The autoinhibitory domain (as a separate peptide) binds the truncated importin-alpha, and the crystal structure of the complex resembles the structure of full-length importin-alpha. Our results support the model of regulation of nuclear import mediated by the intrasteric autoregulatory sequence of importin-alpha and provide a quantitative description of the binding and regulatory steps during nuclear import.
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Affiliation(s)
- B Catimel
- Ludwig Institute for Cancer Research, Royal Melbourne Hospital, Victoria 3050, Australia
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24
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Abstract
Phenylalanine hydroxylase (PAH) is activated by its substrate phenylalanine and inhibited by its cofactor tetrahydrobiopterin (BH(4)). The crystal structure of PAH revealed that the N-terminal sequence of the enzyme (residues 19-29) partially covered the enzyme active site, and suggested its involvement in regulation. We show that the protein lacking this N-terminal sequence does not require activation by phenylalanine, shows an altered structural response to phenylalanine, and is not inhibited by BH(4). Our data support the model where the N-terminal sequence of PAH acts as an intrasteric autoregulatory sequence, responsible for transmitting the effect of phenylalanine activation to the active site.
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Affiliation(s)
- I G Jennings
- Structural Biology Laboratory, St. Vincent's Institute of Medical Research, Fitzroy, Vic., Australia
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25
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Jennings IG, Cotton RG, Kobe B. Functional analysis, using in vitro mutagenesis, of amino acids located in the phenylalanine hydroxylase active site. Arch Biochem Biophys 2000; 384:238-44. [PMID: 11368310 DOI: 10.1006/abbi.2000.2111] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [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
The 3-dimensional structure determination of rat phenylalanine hydroxylase (PAH) has identified potentially important amino acids lining the active site cleft with the majority of these having hydrophobic side-chains including several with aromatic side chains. Here we have analyzed the effect on rat PAH enzyme kinetics of in vitro mutagenesis of a number of these amino acids lining the PAH active site. Mutation of F299, Y324, F331, and Y343 caused a significant decrease in enzyme activity but no change in the Km for substrate or cofactor. We conclude that these aromatic residues are essential for activity but are not significantly involved in binding of the substrate or cofactor. In contrast the PAH mutant, S349T, showed an 18-fold increase in Km for phenylalanine, showing the first functional evidence that this residue was binding at or near the phenylalanine binding site. This confirms the recently published model for the binding of phenylalanine to the PAH active site that postulated S349 interacts with the amino group on the main chain of the phenylalanine molecule. This result differs with that found for the equivalent mutation (S395T), in the closely related tyrosine hydroxylase, which had no effect on substrate Km, showing that while the architecture of the two active sites are very similar the amino acids that bind to the respective substrates are different.
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Affiliation(s)
- I G Jennings
- St. Vincent's Institute of Medical Research, St. Vincent's Hospital, Fitzroy, Victoria, Australia.
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26
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Jennings IG, Cotton RG, Kobe B. Structural interpretation of mutations in phenylalanine hydroxylase protein aids in identifying genotype-phenotype correlations in phenylketonuria. Eur J Hum Genet 2000; 8:683-96. [PMID: 10980574 DOI: 10.1038/sj.ejhg.5200518] [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: 11/09/2022] Open
Abstract
Phenylalanine hydroxylase (PAH) is the enzyme that converts phenylalanine to tyrosine as a rate-limiting step in phenylalanine catabolism and protein and neurotransmitter biosynthesis. Over 300 mutations have been identified in the gene encoding PAH that result in a deficient enzyme activity and lead to the disorders hyperphenylalaninaemia and phenylketonuria. The determination of the crystal structure of PAH now allows the determination of the structural basis of mutations resulting in PAH deficiency. We present an analysis of the structural basis of 120 mutations with a 'classified' biochemical phenotype and/or available in vitro expression data. We find that the mutations can be grouped into five structural categories, based on the distinct expected structural and functional effects of the mutations in each category. Missense mutations and small amino acid deletions are found in three categories: 'active site mutations', 'dimer interface mutations', and 'domain structure mutations'. Nonsense mutations and splicing mutations form the category of 'proteins with truncations and large deletions'. The final category, 'fusion proteins', is caused by frameshift mutations. We show that the structural information helps formulate some rules that will help predict the likely effects of unclassified and newly discovered mutations: proteins with truncations and large deletions, fusion proteins and active site mutations generally cause severe phenotypes; domain structure mutations and dimer interface mutations spread over a range of phenotypes, but domain structure mutations in the catalytic domain are more likely to be severe than domain structure mutations in the regulatory domain or dimer interface mutations.
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Affiliation(s)
- I G Jennings
- Structural Biology Laboratory, St Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia
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27
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Abstract
The recently determined crystal structure of the PR65/A subunit of protein phosphatase 2A reveals the architecture of proteins containing HEAT repeats. The structural properties of this solenoid protein explain many functional characteristics and account for the involvement of solenoids as scaffold, anchoring and adaptor proteins.
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Affiliation(s)
- B Kobe
- Structural Biology Laboratory, St Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia.
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28
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Kobe B, Jennings IG, House CM, Michell BJ, Goodwill KE, Santarsiero BD, Stevens RC, Cotton RG, Kemp BE. Structural basis of autoregulation of phenylalanine hydroxylase. Nat Struct Biol 1999; 6:442-8. [PMID: 10331871 DOI: 10.1038/8247] [Citation(s) in RCA: 175] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Phenylalanine hydroxylase converts phenylalanine to tyrosine, a rate-limiting step in phenylalanine catabolism and protein and neurotransmitter biosynthesis. It is tightly regulated by the substrates phenylalanine and tetrahydrobiopterin and by phosphorylation. We present the crystal structures of dephosphorylated and phosphorylated forms of a dimeric enzyme with catalytic and regulatory properties of the wild-type protein. The structures reveal a catalytic domain flexibly linked to a regulatory domain. The latter consists of an N-terminal autoregulatory sequence (containing Ser 16, which is the site of phosphorylation) that extends over the active site pocket, and an alpha-beta sandwich core that is, unexpectedly, structurally related to both pterin dehydratase and the regulatory domains of metabolic enzymes. Phosphorylation has no major structural effects in the absence of phenylalanine, suggesting that phenylalanine and phosphorylation act in concert to activate the enzyme through a combination of intrasteric and possibly allosteric mechanisms.
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Affiliation(s)
- B Kobe
- St. Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia.
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Hufton SE, Jennings IG, Cotton RG. Structure/function analysis of the domains required for the multimerisation of phenylalanine hydroxylase. Biochim Biophys Acta 1998; 1382:295-304. [PMID: 9540801 DOI: 10.1016/s0167-4838(97)00171-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Phenylalanine hydroxylase (PAH) exists as an equilibrium of dimers and tetramers. However, there is little information concerning the inter- or intra-molecular interactions required for enzyme quaternary structure. It is predicted that the formation of a PAH tetramer will require at least two points of contact per enzyme subunit. Sequence analysis has suggested the existence of a C-terminal domain with characteristics of a leucine zipper or a variant of this called a coiled-coil. By deletion of 24 amino acids from the C-terminus or conversion of leucine 448 to an alanine residue, we have shown that this putative leucine zipper/coiled-coil domain is involved in the assembly of an active enzyme tetramer from dimers. The removal of this C-terminal domain of PAH reduces enzyme activity but does not abolish it. Furthermore, we report that an alanine 447 to aspartate mutation associated with phenylketonuria may affect subunit assembly which suggests the formation of enzyme tetramers is physiologically relevant. Our analysis of subunit interactions in vivo, show that in the absence of the C-terminal coiled-coil domain, dimers can form and this is only possible when the N-terminal domain is present. This provides the first evidence that N-terminal domain is required for multimerisation. We propose that the N-terminal regulatory domain in conjunction with the C-terminal coiled-coil domain, mediates the formation of fully active enzyme tetramers.
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Affiliation(s)
- S E Hufton
- Mutation Research Centre, St. Vincent's Hospital, Fitzroy, Vic., Australia
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Kobe B, Jennings IG, House CM, Feil SC, Michell BJ, Tiganis T, Parker MW, Cotton RG, Kemp BE. Regulation and crystallization of phosphorylated and dephosphorylated forms of truncated dimeric phenylalanine hydroxylase. Protein Sci 1997; 6:1352-7. [PMID: 9194198 PMCID: PMC2143721 DOI: 10.1002/pro.5560060626] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [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: 02/04/2023]
Abstract
Phenylalanine hydroxylase is regulated in a complex manner, including activation by phosphorylation. It is normally found as an equilibrium of dimeric and tetrameric species, with the tetramer thought to be the active form. We converted the protein to the dimeric form by deleting the C-terminal 24 residues and show that the truncated protein remains active and regulated by phosphorylation. This indicates that changes in the tetrameric quaternary structure of phenylalanine hydroxylase are not required for enzyme activation. Truncation also facilitates crystallization of both phosphorylated and dephosphorylated forms of the enzyme.
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Affiliation(s)
- B Kobe
- St. Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia.
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Affiliation(s)
- S E Hufton
- Olive Miller Protein Chemistry Laboratory, Murdoch Institute, Royal Children's Hospital, Parkville, Victoria, Australia
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Dickson PW, Jennings IG, Cotton RG. Delineation of the catalytic core of phenylalanine hydroxylase and identification of glutamate 286 as a critical residue for pterin function. J Biol Chem 1994; 269:20369-75. [PMID: 7914195] [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] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Rat phenylalanine hydroxylase was expressed in Escherichia coli. High level expression was achieved when the transformed E. coli were incubated at 27 degrees C for 24 h. A series of truncated fragments were expressed. The smallest fragment that gave an active soluble protein was from Leu142 to Phe410. This fragment corresponds closely to the region where there is highest homology between the three aromatic amino acid hydroxylases. The circular dichroism spectra of the phenylalanine hydroxylase catalytic core suggested that it contains around 50% alpha-helix. The core fragment is monomeric in dilute solutions but self-associates at higher concentrations. The E. coli expression system was used to generate a number of mutations in phenylalanine hydroxylase from position 264 to 290. This region had been previously shown to be important for pterin binding. Characterization of the mutant phenylalanine hydroxylase molecules identified Glu286 as an amino acid critical for pterin function in phenylalanine hydroxylase.
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Affiliation(s)
- P W Dickson
- Russell Grimwade Laboratory of Protein Engineering, Russell Grimwade School of Biochemistry, University of Melbourne, Parkville, Victoria, Australia
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Cotton RG, Howells DW, Saleeba JA, Dianzani I, Smooker PM, Jennings IG. Structure function studies of the phenylalanine hydroxylase active site and a summary of structural features. Adv Exp Med Biol 1993; 338:55-7. [PMID: 7905699 DOI: 10.1007/978-1-4615-2960-6_10] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- R G Cotton
- Murdoch Institute, Royal Children's Hospital, Parkville, Australia
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Chestkov VV, Shepkina IV, Jennings IG, Cotton RG, Shishkin SS. [Phenylalanine hydroxylase-like antibody in human chorionic villi]. Biull Eksp Biol Med 1992; 114:308-10. [PMID: 1477371] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
An antigen similar by electrophoretic mobility to liver phenylalanine hydroxylase (PH) and cross-reacting with monoclonal antibody PH8 against liver PH was detected in extracts of soluble proteins in 6 from 23 samples of chorionic villi. An antigen with electrophoretic mobility corresponding to 40-41 kDa was detected in extracts of membrane proteins from these 23 samples by immunoblotting with monoclonal antibody PH8. Its molecular weight was similar to that of major chymotryptic peptide of human liver PH. The content of the antigen varied with samples and was less than 20 ng/mg of the extracted protein. Two-dimensional gel electrophoresis revealed only 1 spot of the antigen. The antigen did not react with monoclonal antibodies PH7 and PH9 epitopes of which were located in N-terminal fragment of liver PH. These data suggest that the antigen of membrane fraction could be a PH protein without N-terminal domain.
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Jennings IG, Kemp BE, Cotton RG. Localization of cofactor binding sites with monoclonal anti-idiotype antibodies: phenylalanine hydroxylase. Proc Natl Acad Sci U S A 1991; 88:5734-8. [PMID: 2062852 PMCID: PMC51952 DOI: 10.1073/pnas.88.13.5734] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.0] [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: 12/30/2022] Open
Abstract
A monoclonal anti-idiotype antibody, NS7, previously shown to mimic the binding of the pterin cofactor of phenylalanine hydroxylase (phenylalanine 4-monooxygenase, EC 1.14.16.1) has been used to localize the cofactor binding site within the phenylalanine hydroxylase catalytic domain to a 27-amino-acid sequence that is highly conserved among the three aromatic amino acid hydroxylases. The binding of NS7 to a synthetic peptide corresponding to the phenylalanine hydroxylase sequence from residue 263 to residue 289 was blocked by the competitive inhibitor of phenylalanine hydroxylase enzyme activity, 7,8-dihydro-6,7-dimethylpterin. In addition this peptide competed with native phenylalanine hydroxylase for binding to 6,7-dimethyl-5,6,7,8-tetrahydropterin conjugated to a polyglutamate carrier. Application of this simple and direct approach to other enzymes is likely to greatly facilitate the identification of ligand binding sites on enzymes, which will significantly contribute to the understanding of enzyme structure-function relationships.
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Affiliation(s)
- I G Jennings
- Olive Miller Protein Chemistry Laboratory, Murdoch Institute for Research into Birth Defects, Royal Children's Hospital, Parkville, Victoria, Australia
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Ratnam S, Ratnam M, Cotton RG, Jennings IG, Freisheim JH. Anti-idiotypic antibodies elicited by pterin recognize active site epitopes in dihydrofolate reductases and dihydropteridine reductase. Arch Biochem Biophys 1989; 275:344-53. [PMID: 2480746 DOI: 10.1016/0003-9861(89)90381-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [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: 01/01/2023]
Abstract
Monoclonal antibodies (mAbs) against antipterin immunoglobulin and dihydropteridine reductase (DHPR) and also polyclonal antibodies against human dihydrofolate reductase (DHFR) were obtained. The anti-idiotypic mAbs and anti-DHPR mAbs bind specifically to human DHFR, Escherichia coli DHFR, soybean seedling DHFR, and human DHPR in solid-phase immunoassays. Further, the mAbs bind to the native but not to the denatured forms of DHFRs. The monoclonal antibodies also inhibit the enzymatic activity of human DHFR but not that of human DHPR. Competitive solid-phase immunoassays show stoichiometric inhibition by methotrexate and partial inhibition by NADPH of mAb binding to human DHFR. Cyanogen bromide fragments derived from human DHFR (residues 15-52 and 53-111), containing several active site residues, bind partially to some of the monoclonal antibodies. Accordingly, polyclonal antibodies to peptide 53-111 of human DHFR cross-react to some extent with human DHPR. Data from competitive immunoassays in which the binding of the various mAbs was tested singly and in combination with other mAbs suggest that these antibodies bind to a common region on human DHFR. The results also indicate that the mAbs display some heterogeneity with respect to specific epitopes. These data suggest that despite the absence of significant amino acid sequence homologies among the various DHFRs and DHPR, they have a fundamentally similar topography at the site of binding of the pterin moiety that is recognized by the anti-idiotypic mAbs generated by pterin. In the relatively simple structure of the pterin ring system there are different substituent groups at positions C4 and C6 in methotrexate, 7,8-dihydrofolate, and 7,8-dihydrobiopterin, suggesting that these antibodies are specific for regions on various proteins that interact with the remainder of the pterin moiety. These mAbs and similar mAbs specified by substituent groups on pterin may thus be used as specific probes or inhibitors of various folate-dependent enzymes and transport proteins. They should also provide insights into some of the general features of antibody recognition of protein antigens.
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Affiliation(s)
- S Ratnam
- Department of Biochemistry, Medical College of Ohio, Toledo 43699-0008
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Parniak MA, Jennings IG, Cotton RG. Interaction with a monoclonal antibody alters the expression of co-operativity by phenylalanine hydroxylase from rat liver. Biochem J 1989; 257:383-8. [PMID: 2930457 PMCID: PMC1135591 DOI: 10.1042/bj2570383] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [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: 01/03/2023]
Abstract
Phenylalanine hydroxylase purified from rat liver shows positive co-operativity in response to variations in phenylalanine concentration when assayed with the naturally occurring cofactor tetrahydrobiopterin. In addition, preincubation of phenylalanine hydroxylase with phenylalanine results in a substantial activation of the tetrahydrobiopterin-dependent activity of the enzyme. The monoclonal antibody PH-1 binds to phenylalanine hydroxylase only after the enzyme has been preincubated with phenylalanine and is therefore assumed to recognize a conformational epitope associated with substrate-level activation of the hydroxylase. Under these conditions, PH-1 inhibits the activity of phenylalanine hydroxylase; however, at maximal binding of PH-1 the enzyme is still 2-3 fold activated relative to the native enzyme. The inhibition by PH-1 is non-competitive with respect to tetrahydropterin cofactor. This suggests that PH-1 does not bind to an epitope at the active site of the hydroxylase. Upon maximal binding of PH-1, the positive co-operativity normally expressed by phenylalanine hydroxylase with respect to variations in phenylalanine concentration is abolished. The monoclonal antibody may therefore interact with phenylalanine hydroxylase at or near the regulatory or activator-binding site for phenylalanine on the enzyme molecule.
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Affiliation(s)
- M A Parniak
- Lady Davis Institute for Medical Research, McGill University, Montreal, Quebec, Canada
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Haan EA, Jennings IG, Cuello AC, Nakata H, Fujisawa H, Chow CW, Kushinsky R, Brittingham J, Cotton RG. Identification of serotonergic neurons in human brain by a monoclonal antibody binding to all three aromatic amino acid hydroxylases. Brain Res 1987; 426:19-27. [PMID: 2891407 DOI: 10.1016/0006-8993(87)90420-3] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.0] [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: 01/03/2023]
Abstract
A monoclonal antibody, PH8, has been isolated and shown by immunocytochemistry to bind to serotonergic and catecholaminergic neurons in sections of the rat and human brain. In human brain, obtained at autopsy, particular fixation and embedding conditions eliminate the labelling of catecholaminergic neurons while leaving intact the labelling of serotonergic neurons. This property makes the antibody of potential use for structural studies of serotonergic neurons in the normal and diseased human brain. PH8 was raised to pure monkey phenylalanine hydroxylase and has been shown to bind to the 50,000 mol. wt. phenylalanine hydroxylase polypeptide. Immunocytochemical and immunochemical evidence is presented in support of the hypothesis that the labelling of serotonergic and catecholaminergic neurons results from the binding of PH8 to tryptophan and tyrosine hydroxylase, respectively.
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Affiliation(s)
- E A Haan
- Birth Defects Research Institute, Royal Children's Hospital, Parkville, Australia
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Choo KH, Filby RG, Jennings IG, Peterson G, Fowler K. Vectors for expression and amplification of cDNA in mammalian cells: expression of rat phenylalanine hydroxylase. DNA 1986; 5:529-37. [PMID: 3028740 DOI: 10.1089/dna.1.1986.5.529] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
We have constructed two recombinant plasmid vectors for direct expression and amplification of cDNA in mammalian cells. Each vector carries two dominant selectable markers (the bacterial neo gene and the mouse DHFR gene), a promoter sequence (viral LTR in pAV009/A+, and sheep metallothionein promoter in pMT010/A+), a polyadenylation signal sequence, and a Bam HI site to allow insertion of cDNA. We have used these vectors to prepare recombinant clones for the expression of rat phenylalanine hydroxylase (PH) in LTK- cells. Selection of transformants with neomycin followed by selection of the transformants in methotrexate led to a 30- to 60-fold amplification of the DHFR marker and co-amplification of the PH cDNA, with a corresponding increase in the level of PH mRNA and enzyme polypeptide. The expressed enzyme has a subunit molecular weight of 50,000 which corresponds to the W- allele of rat liver PH. PH activity was detected in the transfected cells by enzymatic measurement of the conversion of [14C]phenylalanine to [14C]tyrosine, and by growth of these cells in a tyrosine-free culture medium. Expression of rat PH in cell culture should facilitate the analysis of the biochemical properties of this enzyme.
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Jennings IG, Russell RG, Armarego WL, Cotton RG. Functional analysis of the effect of monoclonal antibodies on monkey liver phenylalanine hydroxylase. Biochem J 1986; 235:133-8. [PMID: 2427069 PMCID: PMC1146659 DOI: 10.1042/bj2350133] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
An analysis of the effect of eleven monoclonal antibodies on the functional characteristics of monkey liver phenylalanine hydroxylase is presented. These eleven antibodies have been found to react with eight distinct regions on the phenylalanine hydroxylase protein. PH1 antibody inhibits enzyme activity, is dependent on phenylalanine for its binding, and appears to be related to structural changes occurring during phenylalanine activation of the enzyme activity. PH2 and PH3 antibodies stimulate enzyme activity, their binding is inhibited by lysolecithin and this group apparently is recognizing structures involved in lysolecithin activation of the enzyme activity. PH5, PH10, PH12 and PH6 recognise sites on phenylalanine hydroxylase affected by lysolecithin activation.
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Choo KH, Jennings IG, Cotton RG. Comparative studies of four monoclonal antibodies to phenylalanine hydroxylase exhibiting different properties with respect to substrate-dependence, species-specificity and a range of effects on enzyme activity. Biochem J 1981; 199:527-35. [PMID: 6803767 PMCID: PMC1163407 DOI: 10.1042/bj1990527] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Four monoclonal antibodies to phenylalanine hydroxylase are described. Two are inhibitory (PH alpha 1-1 and PH alpha 2-1-1 antibodies), one is stimulatory (B5-1 antibody) and one has no effect on enzyme activity (PH alpha 3-0 antibody). Their properties are compared. Two antibodies (PH alpha 1-1 and B5-1 antibodies) bind primate and rodent phenylalanine hydroxylase, whereas the other two (PH alpha 2-1-1 and PH alpha 3-0 antibodies) bind only the primate enzyme. The binding of PH alpha 1-1 antibody to phenylalanine hydroxylase is dependent on substrate phenylalanine, whereas the binding of the others is not influenced by phenylalanine. Affinity adsorbents prepared from the four antibodies purified phenylalanine hydroxylase substantially (greater than 80% purity) in one step, except for a PH alpha 3-0 antibody--Sepharose column, which behaved anomalously. Two previous publications described the isolation and preliminary characterization of B5 and PH alpha 1-1 antibodies. PH alpha 2-1-1 and PH alpha 3-0 antibodies are reported for the first time.
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Cotton RG, Jennings IG, Choo KH, Fowler K. Isolation and characterization of a myeloma--spleen-cell hybrid producing antibody to phenylalanine hydroxylase. Biochem J 1980; 191:777-83. [PMID: 6793035 PMCID: PMC1162277 DOI: 10.1042/bj1910777] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Application of the technique of myeloma--spleen-cell fusion [Kohler & Milstein (1975) Nature (London) 256, 495--497] has allowed the isolation of a cell colony that produced a monoclonal antibody against monkey liver phenylalanine hydroxylase. The antibody exhibited cross-reactivity against hepatic phenylalanine hydroxylase from other mammalian species, including human, rat and mouse. Cross-reactivity was established by (a) enzyme-inhibition assay, (b) double-immunodiffusion reaction, and (c) two-dimensional polyacrylamide-gel-electrophoretic analysis of immunoprecipitate. The various properties of the monoclonal antibody and its use in the study of mammalian phenylalanine hydroxylase are presented.
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Choo KH, Cotton RG, Jennings IG, Fowler K, Danks DM. Genetics of mammalian phenylalanine hydroxylase system. IV. Evidence of phenylalanine hydroxylase in a cultured human hepatoma cell line. Biochem Genet 1980; 18:955-68. [PMID: 7194638 DOI: 10.1007/bf00500128] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
We report here te identification of a cultured human hepatoma cell line which possesses an active phenylalanine hydroxylase system. Phenylalanine hydroxylation was established by growth of cells in a tyrosine-free medium and by the ability of a cell-free extract to convert [14C]phenylalanine to [14C]tyrosine in an enzyme assay system. This enzyme activity was abolished by the presence in the assay system of p-chlorophenylalanine but no significant effect on the activity was observed with 3-iodotyrosine and 6-fluorotryptophan. Use of antisera against pure monkey or human liver phenylalanine hydroxylase has detected a cross-reacting material in this cell line which is antigenically identical to the human liver enzyme. Phenylalanine hydroxylase purified from this cell line by affinity chromatography revealed a multimeric molecular weight (estimated 275,000) and subunit molecular weights (estimated 50,000 and 49,000) which are similar to those of phenylalanine hydroxylase purified from a normal human liver. This cell line should be a useful tool for the study of the human phenylalanine hydroxylase system.
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Abstract
Rabbit antiserum was prepared against purified normal human liver phenylalanine hydroxylase. This was used to test for cross-reacting material in crude extracts of livers from patients with classical phenylketonuria (PKU); the samples from patients were two livers obtained at autopsy and a needle biopsy core. None of these enzymically inactive livers contained detectable cross-reacting material capable of neutralizing antibody activity in double immunodiffusion and/or enzyme inhibition experiments. In an earlier study, no phenylalanine hydroxylase was found in the two autopsy PKU livers by an affinity chromatography method or by the use of a specific antiserum raised against purified monkey liver phenylalanine hydroxylase (Choo et al., 1979a). This evidence suggests that mutations in th PKU patients studied may be regulatory in nature.
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Choo KH, Cotton RG, Danks DM, Jennings IG. Genetics of the mammalian phenylalanine hydroxylase system. Studies of human liver phenylalanine hydroxylase subunit structure and of mutations in phenylketonuria. Biochem J 1979; 181:285-94. [PMID: 496890 PMCID: PMC1161160 DOI: 10.1042/bj1810285] [Citation(s) in RCA: 37] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Phenylalanine hydroxylase was purified from crude extracts of human livers which show enzyme activity by usine two different methods: (a) affinity chromatography and (b) immunoprecipitation with an antiserum against highly purified monkey liver phenylalanine hydroxylase. Purified human liver phenylalanine hydroxylase has an estimated mol. wt. of 275 000, and subunit mol. wts. of approx. 50 000 and 49 000. These two molecular-weight forms are designated H and L subunits. On two-dimensional polyacrylamide gel under dissociating conditions, enzyme purified by the two methods revealed at least six subunit species, which were resolved into two size classes. Two of these species have a molecular weight corresponding to that of the H subunit, whereas the other four have a molecular weight corresponding to that of the L subunit. This evidence indicates that active phenylalanine hydroxylase purified from human liver is composed of a mixture of sununits which are different in charge and size. None of the subunit species could be detected in crude extracts of livers from two patients with classical phenylketonuria by either the affinity or the immunoprecipitation method. However, they were present in liver from a patient with malignant hyperphenylalaninaemia with normal activity of dihydropteridine reductase.
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Abstract
1. Four independent methods have established that the structure of a previously reported pteridine affinity adsorbent, 6,7-dimethyl-5,6,7,8-tetrahydropterin--CH-Sepharose, is 5(CH-Sepharosyl)-6,7-dimethyl-5,6,7,8-tetrahydropterin. 2. A novel reaction, the carbodiimide-promoted coupling of a carboxyl group to N-5 of a tetrahydropterin, is described. 3. Two novel adsorbents, 5-formyl-tetrahydrofolate--AH-Sepharose and 5-methyl-tetrahydrofolate--AH-Sepharose, are described which may be useful not only in the study of phenylalanine hydroxylase but also in the study of folate-metabolizing enzymes.
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