IUBMB Enzyme Nomenclature


Accepted name: ketol-acid reductoisomerase (NAD+)

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

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

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

Comments: The enzyme, characterized from the bacteria Thermacetogenium phaeum and Desulfococcus oleovorans and from the archaeon Archaeoglobus fulgidus, is specific for NADH [cf. EC, ketol-acid reductoisomerase (NADP+) and EC, ketol-acid reductoisomerase [NAD(P)+]].

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]

Return to EC 1.1.1 home page
Return to EC 1.1 home page
Return to EC 1 home page
Return to Enzymes home page
Return to IUBMB Biochemical Nomenclature home page