IUBMB Enzyme Nomenclature


Accepted name: acetolactate synthase

Reaction: 2 pyruvate = 2-acetolactate + CO2

For diagram click here.

Glossary: thiamine diphosphate

Other name(s): α-acetohydroxy acid synthetase; α-acetohydroxyacid synthase; α-acetolactate synthase; α-acetolactate synthetase; acetohydroxy acid synthetase; acetohydroxyacid synthase; acetolactate pyruvate-lyase (carboxylating); acetolactic synthetase

Systematic name: pyruvate:pyruvate acetaldehydetransferase (decarboxylating)

Comments: This enzyme requires thiamine diphosphate. The reaction shown is in the pathway of biosynthesis of valine; the enzyme can also transfer the acetaldehyde from pyruvate to 2-oxobutanoate, forming 2-ethyl-2-hydroxy-3-oxobutanoate, also known as 2-aceto-2-hydroxybutanoate, a reaction in the biosynthesis of isoleucine.

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 9027-45-6


1. Bauerle, R.H., Freundlich, M., Størmer, F.C. and Umbarger, H.E. Control of isoleucine, valine and leucine biosynthesis. II. Endproduct inhibition by valine of acetohydroxy acid synthetase in Salmonella typhimurium. Biochim. Biophys. Acta 92 (1964) 142-149.

2. Huseby, N.E., Christensen, T.B., Olsen, B.R. and Størmer, F.C. The pH 6 acetolactate-forming enzyme from Aerobacter aerogenes. Subunit structure. Eur. J. Biochem. 20 (1971) 209-214. [PMID: 5560406]

3. Størmer, F.C., Solberg, Y. and Hovig, T. The pH 6 acetolactate-forming enzyme from Aerobacter aerogenes. Molecular properties. Eur. J. Biochem. 10 (1969) 251-260. [PMID: 5823101]

4. Barak, Z., Chipman, D.M. and Gollop, N. Physiological implications of the specificity of acetohydroxy acid synthase isozymes of enteric bacteria. J. Bacteriol. 169 (1987) 3750-3756. [PMID: 3301814]

[EC created 1972 as EC, transferred 2002 to EC]

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