Transaminase

Aminotransferase

Aspartate transaminase from E. coli with Pyridoxal 5' Phosphate cofactor

Identifiers
Symbol| Aminotransferase
Pfam| PF00155
InterPro| IPR004839
Membranome| 273
| Available protein structures:

Pfam | structures / ECOD
PDB| RCSB PDB; PDBe; PDBj
PDBsum| structure summary

Transaminases or aminotransferases are enzymes that catalyze a transamination reaction between an amino acid and an α-keto acid. They are important in the synthesis of amino acids, which form proteins.

Two important transaminase enzymes, aspartate transaminase (AST), and alanine transaminase (ALT), are commonly used as indicators of liver and cardiac health.[1]

## Contents

* 1 Function and mechanism
* 2 Amino acid metabolism in animals
* 2.1 Diagnostic uses
* 3 See also
* 4 References
* 5 Further reading
* 6 External links

## Function and mechanism

Transaminases require the coenzyme pyridoxal phosphate, which is converted into pyridoxamine in the first half-reaction, when an amino acid is converted into a keto acid. Enzyme-bound pyridoxamine in turn reacts with pyruvate, oxaloacetate, or alpha-ketoglutarate, giving alanine, aspartic acid, or glutamic acid, respectively. Many transamination reactions occur in tissues, catalysed by transaminases specific for a particular amino/keto acid pair. The reactions are readily reversible, the direction being determined by which of the reactants are in excess. This reversibility can be exploited for synthetic chemistry applications to achieve the synthesis of valuable chiral amines. The specific enzymes are named from one of the reactant pairs, for example; the reaction between glutamic acid and pyruvic acid to make alpha ketoglutaric acid and alanine is called alanine transaminase and was originally called glutamic-pyruvic transaminase or GPT for short.[2]

Tissue transaminase activities can be investigated by incubating a homogenate with various amino/keto acid pairs. Transamination is demonstrated if the corresponding new amino acid and keto acid are formed, as revealed by paper chromatography. Reversibility is demonstrated by using the complementary keto/amino acid pair as starting reactants. After chromatogram has been taken out of the solvent the chromatogram is then treated with ninhydrin to locate the spots.[3]

Aminotransfer reaction between an amino acid and an alpha-keto acid. The amino (NH2) group and the keto (=O) group are exchanged.

## Amino acid metabolism in animals

### Diagnostic uses

The transaminase enzymes are important in the production of various amino acids, and measuring the concentrations of various transaminases in the blood is important in the diagnosing and tracking many diseases. For example, the presence of elevated transaminases can be an indicator of liver and cardiac damage. Two important transaminase enzymes are aspartate transaminase (AST), also known as serum glutamic oxaloacetic transaminase (SGOT); and alanine transaminase (ALT), also called alanine aminotransferase (ALAT) or serum glutamate-pyruvate transaminase (SGPT). These transaminases were discovered in 1954[2][4][5] and their clinical importance was described in 1955.[6][7][8][9]

## See also

* Valproic acid - a GABA transaminase inhibitor

## References

1. ↑ Vroon DH; Israili Z (1990). "Chapter 99 Aminotransferases". in Walker HK, Hall WD, Hurst JW. Clinical Methods: The History, Physical, and Laboratory Examinations. (3rd ed.). Boston: Butterworths. https://www.ncbi.nlm.nih.gov/books/NBK425/.
2. ↑ 2.0 2.1 "Transaminase activity in human blood". The Journal of Clinical Investigation 34 (1): 126–31. January 1955. doi:10.1172/jci103055. PMID 13221663.
3. ↑ Tulpule, P. G.; Patwardhan, V. N. (April 1952). "Application of Paper Chromatography to the Study of the Transaminase System" (in en). Nature 169 (4303): 671. doi:10.1038/169671a0. ISSN 1476-4687. PMID 14929274. Bibcode: 1952Natur.169..671T. https://www.nature.com/articles/169671a0.
4. ↑ "A note on the spectrometric assay of glutamic-oxalacetic transaminase in human blood serum". The Journal of Clinical Investigation 34 (1): 131–3. January 1955. doi:10.1172/JCI103055. PMID 13221664.
5. ↑ "Serum glutamic oxaloacetic transaminase activity in human acute transmural myocardial infarction". Science 120 (3117): 497–9. September 1954. doi:10.1126/science.120.3117.497. PMID 13195683. Bibcode: 1954Sci...120..497L.
6. ↑ "Biblioteca Nazionale di Napoli. News: Serata in onore di Mario Coltorti e Giuseppe Giusti". http://vecchiosito.bnnonline.it/news/serata.htm.
7. ↑ "E' morto il prof. Coltorti: scoprì le transaminasi". http://notizie-segreteria-liver-pool.blogspot.it/2009/01/e-morto-il-prof-coltorti-scopr-le.html.
8. ↑ "Campania su Coltorti". http://www.istitutobioetica.org/Chi siamo/Campania su Coltorti.htm.
9. ↑ MonrifNet (3 January 2009). "Il Resto Del Carlino - Macerata - E' morto Mario Coltorti: scoprì la transaminasi" (in it). http://www.ilrestodelcarlino.it/macerata/2009/01/03/142193-morto_mario_coltorti_scopri_transaminasi.shtml.

## Further reading

* Ghany, Marc; Hoofnagle, Jay H. (2005). "Approach to the Patient With Liver Disease". Harrison's Principles of Internal Medicine (16th ed.). New York: McGraw-Hill. pp. 1814–5.
* Nelson, David L.; Cox, Michael M. (2000). Lehninger Principles of Biochemistry (3rd ed.). New York: Worth Publishers. pp. 628–31, 634, 828–30.

## External links

* Transaminases at the US National Library of Medicine Medical Subject Headings (MeSH)

* v
* t
* e

Transferase: nitrogenous groups (EC 2.6)

2.6.1: Transaminases|

* Aspartate transaminase
* GOT1
* GOT2
* Alanine transaminase
* GABA transaminase
* Tyrosine aminotransferase
* Kynurenine—oxoglutarate transaminase
* Ornithine aminotransferase
* Branched-chain amino acid aminotransferase
* Alanine—glyoxylate transaminase
* AGXT

2.6.3: Oximinotransferases|

* Oximinotransferase

2.6.99: Other|

* Pyridoxine 5'-phosphate synthase

* v
* t
* e

Enzymes

Activity|

* Active site
* Binding site
* Catalytic triad
* Oxyanion hole
* Enzyme promiscuity
* Catalytically perfect enzyme
* Coenzyme
* Cofactor
* Enzyme catalysis

Regulation|

* Allosteric regulation
* Cooperativity
* Enzyme inhibitor
* Enzyme activator

Classification|

* EC number
* Enzyme superfamily
* Enzyme family
* List of enzymes

Kinetics|

* Enzyme kinetics
* Eadie–Hofstee diagram
* Hanes–Woolf plot
* Lineweaver–Burk plot
* Michaelis–Menten kinetics

Types|

* EC1 Oxidoreductases (list)
* EC2 Transferases (list)
* EC3 Hydrolases (list)
* EC4 Lyases (list)
* EC5 Isomerases (list)
* EC6 Ligases (list)
* EC7 Translocases (list)

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