GOT2

Aspartate aminotransferase, mitochondrial is an enzyme that in humans is encoded by the GOT2 gene. Glutamic-oxaloacetic transaminase is a pyridoxal phosphate-dependent enzyme which exists in cytoplasmic and inner-membrane mitochondrial forms, GOT1 and GOT2, respectively. GOT plays a role in amino acid metabolism and the urea and Kreb's cycle. Also, GOT2 is a major participant in the malate-aspartate shuttle, which is a passage from the cytosol to the mitochondria. The two enzymes are homodimeric and show close homology. GOT2 has been seen to have a role in cell proliferation, especially in terms of tumor growth.

GOT2
Available structures PDB Ortholog search: PDBe RCSB List of PDB id codes 5AX8
Identifiers
Aliases	GOT2, KAT4, KATIV, mitAAT, KYAT4, glutamic-oxaloacetic transaminase 2, DEE82
External IDs	OMIM: 138150; MGI: 95792; HomoloGene: 1572; GeneCards: GOT2; OMA:GOT2 - orthologs
Gene location (Human) Chr. Chromosome 16 (human) Band 16q21 Start 58,707,131 bp End 58,734,342 bp
Gene location (Mouse) Chr. Chromosome 8 (mouse) Band 8 D1|8 47.79 cM Start 96,590,762 bp End 96,615,175 bp
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in muscle of thigh myocardium of left ventricle right ventricle gastrocnemius muscle triceps brachii muscle apex of heart vastus lateralis muscle middle temporal gyrus right auricle glutes Top expressed in muscle of thigh tail of embryo lip primary visual cortex superior frontal gyrus right kidney yolk sac dentate gyrus of hippocampal formation granule cell genital tubercle neural layer of retina More reference expression data BioGPS More reference expression data
Gene ontology Molecular function protein homodimerization activity catalytic activity carboxylic acid binding amino acid binding enzyme binding transaminase activity transferase activity kynurenine-oxoglutarate transaminase activity phospholipid binding L-phenylalanine:2-oxoglutarate aminotransferase activity L-aspartate:2-oxoglutarate aminotransferase activity RNA binding pyridoxal phosphate binding 4-hydroxyglutamate transaminase activity Cellular component perikaryon myelin sheath mitochondrial inner membrane membrane cell surface extracellular exosome mitochondrial matrix plasma membrane mitochondrion T-tubule protein-containing complex sarcolemma Biological process fatty acid transport cellular amino acid biosynthetic process oxaloacetate metabolic process dicarboxylic acid metabolic process lipid transport response to ethanol gluconeogenesis cellular amino acid metabolic process glutamate metabolic process aspartate biosynthetic process L-kynurenine metabolic process biosynthesis glutamate catabolic process to aspartate aspartate catabolic process glutamate catabolic process to 2-oxoglutarate 2-oxoglutarate metabolic process 4-hydroxyproline catabolic process aspartate metabolic process glyoxylate metabolic process transport female pregnancy lactation response to muscle activity response to insulin response to morphine Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 2806 14719 Ensembl ENSG00000125166 ENSMUSG00000031672 UniProt P00505 P05202 RefSeq (mRNA) NM_002080 NM_001286220 NM_010325 RefSeq (protein) NP_001273149 NP_002071 NP_034455 Location (UCSC) Chr 16: 58.71 – 58.73 Mb Chr 8: 96.59 – 96.62 Mb PubMed search
Wikidata
View/Edit Human View/Edit Mouse

Structure

GOT2 is a dimer containing two identical subunits that hold overlapping subunit regions. The top and sides of the enzyme are made up of helices, while the bottom is formed by strands of beta sheets and extended hairpin loops. The subunit itself can be categorized into four different parts: a large domain, which binds pyridoxal-P, a small domain, an NH₂-terminal arm, and a bridge across two domains, which is formed by residues 48-75 and 301-358. Virtually ubiquitous in eukaryotic cells, GOT2 nucleic acid and protein sequences are highly conserved, and its 5’regulatory regions in genomic DNA resemble those of typical house-keeping genes in that, e.g., they lack a TATA box. The GOT2 gene is also located on 16q21 and has an exon count of 10.

Function

In order to produce the energy needed for everyday activities, our body needs to go through the process of glycolysis, which breaks down glucose into pyruvate. In this pathway, one very important part is the reduction of NAD+ to NADH and then the rapid oxidation of NADH back into NAD+. The oxidation phase mainly occurs in the mitochondria as part of the electron transport chain, but the transfer of NADH into the mitochondria from the cytosol is impossible, due to the impermeability of the inner mitochondrial membrane to NADH. Therefore, the malate-aspartate shuttle is needed to transfer reducing equivalents across the mitochondrial membrane for energy production. GOT2 and another enzyme, MDH, are essential for the functioning of the shuttle. GOT2 converts oxaloacetate into aspartate by transamination. This aspartate as well as alpha-ketoglutarate return into the cytosol, which is then converted back to oxaloacetate and glutamate, respectively.

Another function of GOT2 is that it is believed to transaminate kynurenine into kynurenic acid (KYNA) in the brain. The KYNA made by the GOT2 is thought to be an important factor in brain pathology. It is suggested that KYNA synthesized by GOT2 could constitute a common, and mechanistically relevant, feature of the neurotoxicity caused by mitochondrial poisons, such as rotenone, malonate, 1-methyl-4-phenylpyridinium, and 3-nitropropionic acid.

Clinical Significance

In nearly all cancer cells, glycolysis has been seen to be highly elevated to meet their increased energy, biosynthesis, and redox needs. Therefore, the malate-aspartate shuttle promotes the net transfer of cytosolic NADH into mitochondria to ensure a high rate of glycolysis in diverse cancer cell lines. In a study completed in 2008, inhibiting the malate-aspartate shuttle was found to impair the glycolysis process and essentially decreased breast adenocarcinoma cell proliferation. Furthermore, knocking down GOT2 and GOT1 has also been reported to inhibit cell proliferation and colony formation in pancreatic cancer cell lines, suggesting that the GOT enzyme is essential for maintaining a high rate of glycolysis to support rapid tumor cell growth. Also, both glucose and glutamine increase GOT2 3K acetylation in PANC-1 cells and that GOT2 3K acetylation plays a critical role in coordinating glucose and glutamine uptake to provide energy and support cell proliferation and tumor growth. This implies that inhibiting GOT2 3K acetylation may merit exploration as a therapeutic agent especially for pancreatic cancer.

Mutations in this gene have been associated with an early onset infantile encephalopathy.

Interactions

GOT2 has been seen to interact with:

• oxaloacetate
• kynurenine
• aspartate
• alpha-ketoglutarate

Interactive pathway map

Click on genes, proteins and metabolites below to link to respective articles.

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Glycolysis and Gluconeogenesis edit

Further reading

• Doonan S, Barra D, Bossa F (1985). "Structural and genetic relationships between cytosolic and mitochondrial isoenzymes". The International Journal of Biochemistry. 16 (12): 1193–9. doi:10.1016/0020-711X(84)90216-7. PMID 6397370.
• Furuya E, Yoshida Y, Tagawa K (May 1979). "Interaction of mitochondrial aspartate aminotransferase with negatively charged lecithin liposomes". Journal of Biochemistry. 85 (5): 1157–63. PMID 376500.
• Craig IW, Tolley E, Bobrow M, van Heyningen V (1979). "Assignment of a gene necessary for the expression of mitochondrial glutamic-oxaloacetic transaminase in human-mouse hybrid cells". Cytogenetics and Cell Genetics. 22 (1–6): 190–4. doi:10.1159/000130933. PMID 752471.
• Pol S, Bousquet-Lemercier B, Pavé-Preux M, Bulle F, Passage E, Hanoune J, Mattei MG, Barouki R (Sep 1989). "Chromosomal localization of human aspartate aminotransferase genes by in situ hybridization". Human Genetics. 83 (2): 159–64. doi:10.1007/BF00286710. PMID 2777255. S2CID 30300621.
• Fahien LA, Kmiotek EH, MacDonald MJ, Fibich B, Mandic M (Aug 1988). "Regulation of malate dehydrogenase activity by glutamate, citrate, alpha-ketoglutarate, and multienzyme interaction". The Journal of Biological Chemistry. 263 (22): 10687–97. doi:10.1016/S0021-9258(18)38026-8. PMID 2899080.
• Pol S, Bousquet-Lemercier B, Pave-Preux M, Pawlak A, Nalpas B, Berthelot P, Hanoune J, Barouki R (Dec 1988). "Nucleotide sequence and tissue distribution of the human mitochondrial aspartate aminotransferase mRNA". Biochemical and Biophysical Research Communications. 157 (3): 1309–15. doi:10.1016/S0006-291X(88)81017-9. PMID 3207426.
• Fahien LA, Kmiotek EH, Woldegiorgis G, Evenson M, Shrago E, Marshall M (May 1985). "Regulation of aminotransferase-glutamate dehydrogenase interactions by carbamyl phosphate synthase-I, Mg2+ plus leucine versus citrate and malate". The Journal of Biological Chemistry. 260 (10): 6069–79. doi:10.1016/S0021-9258(18)88939-6. PMID 3997814.
• Martini F, Angelaccio S, Barra D, Pascarella S, Maras B, Doonan S, Bossa F (Nov 1985). "The primary structure of mitochondrial aspartate aminotransferase from human heart". Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology. 832 (1): 46–51. doi:10.1016/0167-4838(85)90172-4. PMID 4052435.
• Davidson RG, Cortner JA, Rattazzi MC, Ruddle FH, Lubs HA (Jul 1970). "Genetic polymorphisms of human mitochondrial glutamic oxaloacetic transaminase". Science. 169 (3943): 391–2. Bibcode:1970Sci...169..391D. doi:10.1126/science.169.3943.391. PMID 5450376. S2CID 1981940.
• Ford GC, Eichele G, Jansonius JN (May 1980). "Three-dimensional structure of a pyridoxal-phosphate-dependent enzyme, mitochondrial aspartate aminotransferase". Proceedings of the National Academy of Sciences of the United States of America. 77 (5): 2559–63. Bibcode:1980PNAS...77.2559F. doi:10.1073/pnas.77.5.2559. PMC 349441. PMID 6930651.
• Jeremiah SJ, Povey S, Burley MW, Kielty C, Lee M, Spowart G, Corney G, Cook PJ (May 1982). "Mapping studies on human mitochondrial glutamate oxaloacetate transaminase". Annals of Human Genetics. 46 (Pt 2): 145–52. doi:10.1111/j.1469-1809.1982.tb00705.x. PMID 7114792. S2CID 33651132.
• Tolley E, van Heyningen V, Brown R, Bobrow M, Craig IW (Oct 1980). "Assignment to chromosome 16 of a gene necessary for the expression of human mitochondrial glutamate oxaloacetate transaminase (aspartate aminotransferase) (E.C. 2.6.1.1.)". Biochemical Genetics. 18 (9–10): 947–54. doi:10.1007/BF00500127. PMID 7225087. S2CID 9028483.
• Lain B, Iriarte A, Mattingly JR, Moreno JI, Martinez-Carrion M (Oct 1995). "Structural features of the precursor to mitochondrial aspartate aminotransferase responsible for binding to hsp70". The Journal of Biological Chemistry. 270 (42): 24732–9. doi:10.1074/jbc.270.42.24732. PMID 7559589.
• Maruyama K, Sugano S (Jan 1994). "Oligo-capping: a simple method to replace the cap structure of eukaryotic mRNAs with oligoribonucleotides". Gene. 138 (1–2): 171–4. doi:10.1016/0378-1119(94)90802-8. PMID 8125298.
• Suzuki Y, Yoshitomo-Nakagawa K, Maruyama K, Suyama A, Sugano S (Oct 1997). "Construction and characterization of a full length-enriched and a 5'-end-enriched cDNA library". Gene. 200 (1–2): 149–56. doi:10.1016/S0378-1119(97)00411-3. PMID 9373149.