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Kumar I, Silva M, Choudhary DA, Ali SF, Rusak R, Cotzomi P, Wiecek S, Sato I, Khundoker R, Donmez B, Gabriel S, Bobila M, Leonida MD, Traba C. Small molecular exogenous modulators of active forms of MMPs. Biochimie 2023:S0300-9084(23)00292-4. [PMID: 37944661 DOI: 10.1016/j.biochi.2023.10.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Revised: 09/13/2023] [Accepted: 10/31/2023] [Indexed: 11/12/2023]
Abstract
Matrix metalloproteinases (MMPs) are endopeptidases, and their activity depends on calcium and zinc metal ions. These enzymes are expressed originally in zymogenic form, where the active site of proteins is closed by a prodomain which is removed during activation. A homeostatic balance of their activity is primarily regulated by a 'cysteine switch' located on a consensus sequence of the prodomain and natural endogenous inhibitors, called tissue inhibitors of metalloproteinases (TIMPs). Breakage of this homeostasis may lead to various pathological conditions, which may require further activation and/or inhibition of these enzymes to regenerate that balance. Here, we report four modulators, more specifically, three inhibitors (I1, I2 and I3), and one exogenous activator (L) of the active form of human collagenase MMP-1 (without prodomain). The results were confirmed by binding studies using fluorescence-based enzyme assays.
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Affiliation(s)
- Ish Kumar
- Department of Chemistry, Biochemistry & Physics, Fairleigh Dickinson University, 1000 River Rd, Teaneck, NJ, 07666, USA.
| | - Melissa Silva
- Department of Chemistry, Biochemistry & Physics, Fairleigh Dickinson University, 1000 River Rd, Teaneck, NJ, 07666, USA
| | - Dinesh A Choudhary
- Department of Chemistry, Biochemistry & Physics, Fairleigh Dickinson University, 1000 River Rd, Teaneck, NJ, 07666, USA
| | - Syeda F Ali
- Department of Chemistry, Biochemistry & Physics, Fairleigh Dickinson University, 1000 River Rd, Teaneck, NJ, 07666, USA
| | - Raymond Rusak
- Department of Chemistry, Biochemistry & Physics, Fairleigh Dickinson University, 1000 River Rd, Teaneck, NJ, 07666, USA
| | - Paulina Cotzomi
- Department of Chemistry, Biochemistry & Physics, Fairleigh Dickinson University, 1000 River Rd, Teaneck, NJ, 07666, USA
| | - Suzanne Wiecek
- Department of Chemistry, Biochemistry & Physics, Fairleigh Dickinson University, 1000 River Rd, Teaneck, NJ, 07666, USA
| | - Iwon Sato
- Department of Chemistry, Biochemistry & Physics, Fairleigh Dickinson University, 1000 River Rd, Teaneck, NJ, 07666, USA
| | - Rinat Khundoker
- Department of Chemistry, Biochemistry & Physics, Fairleigh Dickinson University, 1000 River Rd, Teaneck, NJ, 07666, USA
| | - Bora Donmez
- Department of Chemistry, Biochemistry & Physics, Fairleigh Dickinson University, 1000 River Rd, Teaneck, NJ, 07666, USA
| | - Samantha Gabriel
- Department of Chemistry, Biochemistry & Physics, Fairleigh Dickinson University, 1000 River Rd, Teaneck, NJ, 07666, USA
| | - Monica Bobila
- Department of Chemistry, Biochemistry & Physics, Fairleigh Dickinson University, 1000 River Rd, Teaneck, NJ, 07666, USA
| | - Mihaela D Leonida
- Department of Chemistry, Biochemistry & Physics, Fairleigh Dickinson University, 1000 River Rd, Teaneck, NJ, 07666, USA
| | - Christian Traba
- Department of Chemistry, Biochemistry & Physics, Fairleigh Dickinson University, 1000 River Rd, Teaneck, NJ, 07666, USA
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2
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Pan C, Mao S, Xiong Z, Chen Z, Xu N. Glutamate dehydrogenase: Potential therapeutic targets for neurodegenerative disease. Eur J Pharmacol 2023; 950:175733. [PMID: 37116563 DOI: 10.1016/j.ejphar.2023.175733] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2022] [Revised: 03/31/2023] [Accepted: 04/17/2023] [Indexed: 04/30/2023]
Abstract
Glutamate dehydrogenase (GDH) is a key enzyme in mammalian glutamate metabolism. It is located at the intersection of multiple metabolic pathways and participates in a variety of cellular activities. GDH activity is strictly regulated by a variety of allosteric compounds. Here, we review the unique distribution and expressions of GDH in the brain nervous system. GDH plays an essential role in the glutamate-glutamine-GABA cycle between astrocytes and neurons. The dysfunction of GDH may induce the occurrence of many neurodegenerative diseases, such as Parkinson's disease, epilepsy, Alzheimer's disease, schizophrenia, and frontotemporal dementia. GDH activators and gene therapy have been found to protect neurons and improve motor disorders in neurodegenerative diseases caused by glutamate metabolism disorders. To date, no medicine has been discovered that specifically targets neurodegenerative diseases, although several potential medicines are used clinically. Targeting GDH to treat neurodegenerative diseases is expected to provide new insights and treatment strategies.
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Affiliation(s)
- Chuqiao Pan
- College of Pharmaceutical Science, Institute of Drug Development & Chemical Biology, Zhejiang University of Technology, Huzhou, 313200, Zhejiang, People's Republic of China
| | - Shijie Mao
- College of Pharmaceutical Science, Institute of Drug Development & Chemical Biology, Zhejiang University of Technology, Huzhou, 313200, Zhejiang, People's Republic of China
| | - Zeping Xiong
- Department of Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals, Zhejiang University of Technology, Huzhou, 313200, Zhejiang, People's Republic of China
| | - Zhao Chen
- College of Pharmaceutical Science, Institute of Drug Development & Chemical Biology, Zhejiang University of Technology, Huzhou, 313200, Zhejiang, People's Republic of China
| | - Ning Xu
- College of Pharmaceutical Science, Institute of Drug Development & Chemical Biology, Zhejiang University of Technology, Huzhou, 313200, Zhejiang, People's Republic of China.
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3
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Bian Y, Hou W, Chen X, Fang J, Xu N, Ruan BH. Glutamate Dehydrogenase as a Promising Target for Hyperinsulinism Hyperammonemia Syndrome Therapy. Curr Med Chem 2021; 29:2652-2672. [PMID: 34525914 DOI: 10.2174/0929867328666210825105342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Revised: 06/17/2021] [Accepted: 06/21/2021] [Indexed: 11/22/2022]
Abstract
Hyperinsulinism-hyperammonemia syndrome (HHS) is a rare disease characterized by recurrent hypoglycemia and persistent elevation of plasma ammonia, and it can lead to severe epilepsy and permanent brain damage. It has been demonstrated that functional mutations of glutamate dehydrogenase (GDH), an enzyme in the mitochondrial matrix, are responsible for the HHS. Thus, GDH has become a promising target for the small molecule therapeutic intervention of HHS. Several medicinal chemistry studies are currently aimed at GDH, however, to date, none of the compounds reported has been entered clinical trials. This perspective summarizes the progress in the discovery and development of GDH inhibitors, including the pathogenesis of HHS, potential binding sites, screening methods, and research models. Future therapeutic perspectives are offered to provide a reference for discovering potent GDH modulators and encourage additional research that will provide more comprehensive guidance for drug development.
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Affiliation(s)
- Yunfei Bian
- College of Pharmaceutical Science, Institute of Drug Development & Chemical Biology, Zhejiang University of Technology, Hantgzhou 310014. China
| | - Wei Hou
- College of Pharmaceutical Science, Institute of Drug Development & Chemical Biology, Zhejiang University of Technology, Hantgzhou 310014. China
| | - Xinrou Chen
- College of Pharmaceutical Science, Institute of Drug Development & Chemical Biology, Zhejiang University of Technology, Hantgzhou 310014. China
| | - Jinzhang Fang
- College of Pharmaceutical Science, Institute of Drug Development & Chemical Biology, Zhejiang University of Technology, Hantgzhou 310014. China
| | - Ning Xu
- College of Pharmaceutical Science, Institute of Drug Development & Chemical Biology, Zhejiang University of Technology, Hantgzhou 310014. China
| | - Benfang Helen Ruan
- College of Pharmaceutical Science, Institute of Drug Development & Chemical Biology, Zhejiang University of Technology, Hantgzhou 310014. China
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4
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Park CK, Horton NC. Structures, functions, and mechanisms of filament forming enzymes: a renaissance of enzyme filamentation. Biophys Rev 2019; 11:927-994. [PMID: 31734826 PMCID: PMC6874960 DOI: 10.1007/s12551-019-00602-6] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Accepted: 10/24/2019] [Indexed: 12/19/2022] Open
Abstract
Filament formation by non-cytoskeletal enzymes has been known for decades, yet only relatively recently has its wide-spread role in enzyme regulation and biology come to be appreciated. This comprehensive review summarizes what is known for each enzyme confirmed to form filamentous structures in vitro, and for the many that are known only to form large self-assemblies within cells. For some enzymes, studies describing both the in vitro filamentous structures and cellular self-assembly formation are also known and described. Special attention is paid to the detailed structures of each type of enzyme filament, as well as the roles the structures play in enzyme regulation and in biology. Where it is known or hypothesized, the advantages conferred by enzyme filamentation are reviewed. Finally, the similarities, differences, and comparison to the SgrAI endonuclease system are also highlighted.
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Affiliation(s)
- Chad K. Park
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ 85721 USA
| | - Nancy C. Horton
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ 85721 USA
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5
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Nassar OM, Wong KY, Lynch GC, Smith TJ, Pettitt BM. Allosteric discrimination at the NADH/ADP regulatory site of glutamate dehydrogenase. Protein Sci 2019; 28:2080-2088. [PMID: 31610054 DOI: 10.1002/pro.3748] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Revised: 09/25/2019] [Accepted: 10/09/2019] [Indexed: 12/14/2022]
Abstract
Glutamate dehydrogenase (GDH) is a target for treating insulin-related disorders, such as hyperinsulinism hyperammonemia syndrome. Modeling native ligand binding has shown promise in designing GDH inhibitors and activators. Our computational investigation of the nicotinamide adenine diphosphate hydride (NADH)/adenosine diphosphate (ADP) site presented in this paper provides insight into the opposite allosteric effects induced at a single site of binding inhibitor NADH versus activator ADP to GDH. The computed binding free-energy difference between NADH and ADP using thermodynamic integration is -0.3 kcal/mol, which is within the -0.275 and -1.7 kcal/mol experimental binding free-energy difference range. Our simulations show an interesting model of ADP with dissimilar binding conformations at each NADH/ADP site in the GDH trimer, which explains the poorly understood strong binding but weak activation shown in experimental studies. In contrast, NADH showed similar inhibitory binding conformations at each NADH/ADP site. The structural analysis of the important residues in the NADH/ADP binding site presented in this paper may provide potential targets for mutation studies for allosteric drug design.
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Affiliation(s)
- Omneya M Nassar
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, Texas
| | - Ka-Yiu Wong
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas
| | - Gillian C Lynch
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas
| | - Thomas J Smith
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas
| | - B Montgomery Pettitt
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, Texas.,Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas
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6
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Kezos JN, Phillips MA, Thomas MD, Ewunkem AJ, Rutledge GA, Barter TT, Santos MA, Wong BD, Arnold KR, Humphrey LA, Yan A, Nouzille C, Sanchez I, Cabral LG, Bradley TJ, Mueller LD, Graves JL, Rose MR. Genomics of Early Cardiac Dysfunction and Mortality in Obese Drosophila melanogaster. Physiol Biochem Zool 2019; 92:591-611. [PMID: 31603376 DOI: 10.1086/706099] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
In experimental evolution, we impose functional demands on laboratory populations of model organisms using selection. After enough generations of such selection, the resulting populations constitute excellent material for physiological research. An intense selection regime for increased starvation resistance was imposed on 10 large outbred Drosophila populations. We observed the selection responses of starvation and desiccation resistance, metabolic reserves, and heart robustness via electrical pacing. Furthermore, we sequenced the pooled genomes of these populations. As expected, significant increases in starvation resistance and lipid content were found in our 10 intensely selected SCO populations. The selection regime also improved desiccation resistance, water content, and glycogen content among these populations. Additionally, the average rate of cardiac arrests in our 10 obese SCO populations was double the rate of the 10 ancestral CO populations. Age-specific mortality rates were increased at early adult ages by selection. Genomic analysis revealed a large number of single nucleotide polymorphisms across the genome that changed in frequency as a result of selection. These genomic results were similar to those obtained in our laboratory from less direct selection procedures. The combination of extensive genomic and phenotypic differentiation between these 10 populations and their ancestors makes them a powerful system for the analysis of the physiological underpinnings of starvation resistance.
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7
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Hoffpauir ZA, Sherman E, Smith TJ. Dissecting the Antenna in Human Glutamate Dehydrogenase: Understanding Its Role in Subunit Communication and Allosteric Regulation. Biochemistry 2019; 58:4195-4206. [PMID: 31577135 DOI: 10.1021/acs.biochem.9b00722] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Glutamate dehydrogenase (GDH) is a homohexameric enzyme that catalyzes the reversible oxidative deamination of l-glutamate. While GDH is found in all living organisms, only that from animals is highly allosterically regulated by a wide array of metabolites. Because only animal GDH has a 50-residue antenna domain, we hypothesized that it was critical for allostery. To this end, we previously replaced the antenna with the loop found in bacteria, and the resulting chimera was no longer regulated by purine nucleotides. Hence, it seemed logical that the purpose of the antenna is to exert the subunit communication necessary for heterotrophic allosteric regulation. Here, we revisit the antenna deletion studies by retaining 10 more of the human GDH (hGDH) residues without adding the bacterial loop. Unexpectedly, the results were profoundly different than before. The basal activity of the mutant is only ∼13% of that of the wild type but ∼100 times more sensitive to all allosteric activators. In contrast, the mutant is still affected by all of the tested inhibitors to approximately the same degree. The resulting antenna-less mutant retained its negative cooperativity with respect to the coenzyme, again suggesting that intersubunit communication is intact. Finally, the mutant still exhibits substrate inhibition, albeit there are differences in the details. We present a model in which the majority of the antenna is not directly involved in allosteric regulation per se but rather may be responsible for improving enzymatic efficiency by acting as a conduit for substrate binding energy between subunits.
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Affiliation(s)
- Zoe A Hoffpauir
- Department of Biochemistry and Molecular Biology , University of Texas Medical Branch at Galveston , 301 University Boulevard, Route 0645 , Galveston , Texas 77555 , United States
| | - Eleena Sherman
- Department of Biochemistry and Molecular Biology , University of Texas Medical Branch at Galveston , 301 University Boulevard, Route 0645 , Galveston , Texas 77555 , United States
| | - Thomas J Smith
- Department of Biochemistry and Molecular Biology , University of Texas Medical Branch at Galveston , 301 University Boulevard, Route 0645 , Galveston , Texas 77555 , United States
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8
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Nassar OM, Li C, Stanley CA, Pettitt BM, Smith TJ. Glutamate dehydrogenase: Structure of a hyperinsulinism mutant, corrections to the atomic model, and insights into a regulatory site. Proteins 2018; 87:41-50. [PMID: 30367518 DOI: 10.1002/prot.25620] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 10/10/2018] [Accepted: 10/16/2018] [Indexed: 11/06/2022]
Abstract
Mammalian glutamate dehydrogenase (GDH) has complex allosteric regulation and the loss of GTP inhibition causes the hyperinsulinism/hyperammonemia syndrome (HHS) where insulin is hypersecreted upon consumption of protein. The archetypical HHS lesion is H454Y and lies in the GTP binding pocket. To better understand the mechanism of HHS, we determined the crystal structure of H454Y. When the bovine GDH crystal structures were minimized to prepare for further computational analysis, unusually large deviations were found at the allosteric NADH binding site due to chemical sequence errors. Notably, 387 lies in an allosteric where several activators and inhibitors bind and should be lysine rather than asparagine. All structures were re-refined and the consequence of this sequence error on NADH binding was calculated using free energy perturbation. The binding free energy penalty going from the correct to incorrect sequence found is +5 kcal/mol per site and therefore has a significant impact on drug development. BROADER AUDIENCE ABSTRACT: Glutamate dehydrogenase is a key enzyme involved in amino acid catabolism. As such, it is heavily regulated in animals by a wide array of metabolites. The importance of this regulation is most apparent in a genetic disorder called hyperinsulinism/hyperammonemia (HHS) where patients hypersecrete insulin upon the consumption of protein. We determined the atomic structure of one of these HHS mutants to better understand the disease and also analyzed an allosteric regulatory site.
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Affiliation(s)
- Omneya M Nassar
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, Texas
| | - Changhong Li
- Division of Endocrinology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Charles A Stanley
- Division of Endocrinology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - B Montgomery Pettitt
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, Texas.,Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas
| | - Thomas J Smith
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas
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Sivanesan S, Taylor A, Zhang J, Bakovic M. Betaine and Choline Improve Lipid Homeostasis in Obesity by Participation in Mitochondrial Oxidative Demethylation. Front Nutr 2018; 5:61. [PMID: 30042948 PMCID: PMC6048254 DOI: 10.3389/fnut.2018.00061] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Accepted: 06/21/2018] [Indexed: 01/01/2023] Open
Abstract
We investigated the metabolic effects of betaine (Bet) supplementation on CTP:phosphoethanolamine cytidylyltransferase/Pcyt2 heterozygous mice (HET). HET received either no treatment or were allowed access to 1% Bet supplemented water for 8 weeks. As we previously showed with choline (Cho), Bet improved hypertriglyceridemia, and hepatic steatosis in HET. The protection from obesity associated with reduced hepatic steatosis and increased lipid breakdown in adipocytes was attributed to increased energy requirements for metabolism and elimination of supplemented Bet and Cho. 1H-NMR-based profiling revealed metabolic changes caused by Bet and Cho supplementation. Cho increased the citric acid cycle intermediate succinic acid while reducing isoleucine, valine, threonine, and lysine. Bet increased α-ketoglutaric acid and did not stimulate catabolism of amino acids. Increased histidine and alanine are specific biomarkers for Bet treatment. Cho and Bet caused glycerol accumulation and reduced sarcosine, taurine, acetate, and β-hydroxybutyrate levels. These data provide new insights on how Cho and Bet supplementation can aid in treatment of obesity related disorders due to their positive effects on lipolysis, the citric acid cycle, and mitochondrial oxidative demethylation.
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Affiliation(s)
- Sugashan Sivanesan
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON, Canada
| | - Adrian Taylor
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON, Canada
| | - Junzeng Zhang
- Aquatic and Crop Resource Development, National Research Council Canada, Halifax, NS, Canada
| | - Marica Bakovic
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON, Canada
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10
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Smith HQ, Li C, Stanley CA, Smith TJ. Glutamate Dehydrogenase, a Complex Enzyme at a Crucial Metabolic Branch Point. Neurochem Res 2017; 44:117-132. [PMID: 29079932 DOI: 10.1007/s11064-017-2428-0] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2017] [Revised: 10/17/2017] [Accepted: 10/21/2017] [Indexed: 12/27/2022]
Abstract
In-vitro, glutamate dehydrogenase (GDH) catalyzes the reversible oxidative deamination of glutamate to α-ketoglutarate (α-KG). GDH is found in all organisms, but in animals is allosterically regulated by a wide array of metabolites. For many years, it was not at all clear why animals required such complex control. Further, in both standard textbooks and some research publications, there has been some controversy as to the directionality of the reaction. Here we review recent work demonstrating that GDH operates mainly in the catabolic direction in-vivo and that the finely tuned network of allosteric regulators allows GDH to meet the varied needs in a wide range of tissues in animals. Finally, we review the progress in using pharmacological agents to activate or inhibit GDH that could impact a wide range of pathologies from insulin disorders to tumor growth.
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Affiliation(s)
- Hong Q Smith
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch at Galveston, Galveston, TX, USA
| | - Changhong Li
- Division of Endocrinology, The Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Charles A Stanley
- Division of Endocrinology, The Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Thomas James Smith
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch at Galveston, Galveston, TX, USA.
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11
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Lu M, Li C. Nutrient sensing in pancreatic islets: lessons from congenital hyperinsulinism and monogenic diabetes. Ann N Y Acad Sci 2017; 1411:65-82. [PMID: 29044608 DOI: 10.1111/nyas.13448] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Revised: 07/05/2017] [Accepted: 07/14/2017] [Indexed: 12/14/2022]
Abstract
Pancreatic beta cells sense changes in nutrients during the cycles of fasting and feeding and release insulin accordingly to maintain glucose homeostasis. Abnormal beta cell nutrient sensing resulting from gene mutations leads to hypoglycemia or diabetes. Glucokinase (GCK) plays a key role in beta cell glucose sensing. As one form of congenital hyperinsulinism (CHI), activating mutations of GCK result in a decreased threshold for glucose-stimulated insulin secretion and hypoglycemia. In contrast, inactivating mutations of GCK result in diabetes, including a mild form (MODY2) and a severe form (permanent neonatal diabetes mellitus (PNDM)). Mutations of beta cell ion channels involved in insulin secretion regulation also alter glucose sensing. Activating or inactivating mutations of ATP-dependent potassium (KATP ) channel genes result in severe but completely opposite clinical phenotypes, including PNDM and CHI. Mutations of the other ion channels, including voltage-gated potassium channels (Kv 7.1) and voltage-gated calcium channels, also lead to abnormal glucose sensing and CHI. Furthermore, amino acids can stimulate insulin secretion in a glucose-independent manner in some forms of CHI, including activating mutations of the glutamate dehydrogenase gene, HDAH deficiency, and inactivating mutations of KATP channel genes. These genetic defects have provided insight into a better understanding of the complicated nature of beta cell fuel-sensing mechanisms.
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Affiliation(s)
- Ming Lu
- Division of Endocrinology and Diabetes, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.,Department of Pediatrics & Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.,Department of Endocrinology, Shandong Provincial Hospital affiliated to Shandong University, Jinan, Shandong, China
| | - Changhong Li
- Division of Endocrinology and Diabetes, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.,Department of Pediatrics & Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
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12
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Abstract
Pancreatic islet β cells secrete insulin in response to nutrient secretagogues, like glucose, dependent on calcium influx and nutrient metabolism. One of the most intriguing qualities of β cells is their ability to use metabolism to amplify the amount of secreted insulin independent of further alterations in intracellular calcium. Many years studying this amplifying process have shaped our current understanding of β cell stimulus-secretion coupling; yet, the exact mechanisms of amplification have been elusive. Recent studies utilizing metabolomics, computational modeling, and animal models have progressed our understanding of the metabolic amplifying pathway of insulin secretion from the β cell. New approaches will be discussed which offer in-roads to a more complete model of β cell function. The development of β cell therapeutics may be aided by such a model, facilitating the targeting of aspects of the metabolic amplifying pathway which are unique to the β cell.
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Affiliation(s)
- Michael A Kalwat
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX, United States.
| | - Melanie H Cobb
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX, United States
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