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)+]].
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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