IUBMB Enzyme Nomenclature


Accepted name: ketol-acid reductoisomerase [NAD(P)+]

Reaction: (2R)-2,3-dihydroxy-3-methylbutanoate + NAD(P)+ = (2S)-2-hydroxy-2-methyl-3-oxobutanoate + NAD(P)H + H+

Glossary: (2S)-2-hydroxy-2-methyl-3-oxobutanoate = (2S)-2-acetolactate

Systematic name: (2R)-2,3-dihydroxy-3-methylbutanoate:NAD(P)+ oxidoreductase (isomerizing)

Comments: The enzyme, characterized from the bacteria Hydrogenobaculum sp. and Syntrophomonas wolfei subsp. wolfei and from the archaea Metallosphaera sedula and Ignisphaera aggregans, can use both NADH and NADPH with similar efficiency [cf. EC, ketol-acid reductoisomerase (NADP+) and EC, ketol-acid reductoisomerase (NAD+)].

Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:


1. Brinkmann-Chen, S., Cahn, J.K. and Arnold, F.H. Uncovering rare NADH-preferring ketol-acid reductoisomerases. Metab. Eng. 26C (2014) 17-22. [PMID: 25172159]

[EC created 2015]

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