Ketol-acid reductoisomerase

Thus, the two substrates of this enzyme are (R)-2,3-dihydroxy-3-methylbutanoate and NADP⁺, whereas its 3 products are (S)-2-hydroxy-2-methyl-3-oxobutanoate, NADPH, and H⁺.

This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD⁺ or NADP⁺ as acceptor. The systematic name of this enzyme class is (R)-2,3-dihydroxy-3-methylbutanoate:NADP⁺ oxidoreductase (isomerizing). Other names in common use include dihydroxyisovalerate dehydrogenase (isomerizing), acetohydroxy acid isomeroreductase, ketol acid reductoisomerase, alpha-keto-beta-hydroxylacyl reductoisomerase, 2-hydroxy-3-keto acid reductoisomerase, acetohydroxy acid reductoisomerase, acetolactate reductoisomerase, dihydroxyisovalerate (isomerizing) dehydrogenase, isomeroreductase, and reductoisomerase. This enzyme participates in valine, leucine and isoleucine biosynthesis and pantothenate and coa biosynthesis.

Structural studies

As of late 2007, 4 structures have been solved for this class of enzymes, with PDB accession codes 1NP3, 1QMG, 1YRL, and 1YVE.

References

Arfin SM, Umbarger HE (1969). "Purification and properties of the acetohydroxy acid isomeroreductase of Salmonella typhimurium". J. Biol. Chem. 244 (5): 1118–27. PMID 4388025.
Hill RK, Sawada S and Arfin SM (1979). "Stereochemistry of valine and isoleucine biosynthesis. IV Synthesis, configuration, and enzymatic specificity of alpha-acetolactate and alpha-aceto-alpha-hydroxybutyrate". Bioorg. Chem. 8 (2): 175–189. doi:10.1016/0045-2068(79)90003-8.
Kiritani K, Narise S and Wagner RP (1966). "The reductoisomerase of Neurospora crassa". J. Biol. Chem. 241: 2047–2051.
Satyanarayana T, Radhakrishnan AN (1965). "Biosynthesis of valine and isoleucine in plants. 3. Reductoisomerase of Phaseolus radiatus". Biochim. Biophys. Acta 110 (2): 380–8. doi:10.1016/s0926-6593(65)80045-5. PMID 5866387.

Oxidoreductases: alcohol oxidoreductases (EC 1.1)

1.1.1: NAD/NADP acceptor	3-hydroxyacyl-CoA dehydrogenase 3-hydroxybutyryl-CoA dehydrogenase Alcohol dehydrogenase Aldo-keto reductase 1A1 1B1 1B10 1C1 1C3 1C4 7A2 Aldose reductase Beta-Ketoacyl ACP reductase Carbohydrate dehydrogenases Carnitine dehydrogenase D-malate dehydrogenase (decarboxylating) DXP reductoisomerase Glucose-6-phosphate dehydrogenase Glycerol-3-phosphate dehydrogenase HMG-CoA reductase IMP dehydrogenase Isocitrate dehydrogenase Lactate dehydrogenase L-threonine dehydrogenase L-xylulose reductase Malate dehydrogenase Malate dehydrogenase (decarboxylating) Malate dehydrogenase (NADP+) Malate dehydrogenase (oxaloacetate-decarboxylating) Malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+) Phosphogluconate dehydrogenase Sorbitol dehydrogenase Hydroxysteroid dehydrogenase: 3 Beta 3-beta-HSD NSDHL 11 Beta HSD11B1 HSD11B2 17 Beta

1.1.2: cytochrome acceptor	D-lactate dehydrogenase (cytochrome) D-lactate dehydrogenase (cytochrome c-553) Mannitol dehydrogenase (cytochrome)

1.1.3: oxygen acceptor	Glucose oxidase L-gulonolactone oxidase Xanthine oxidase

1.1.4: disulfide as acceptor	Vitamin K epoxide reductase Vitamin-K-epoxide reductase (warfarin-insensitive)

1.1.5: quinone/similar acceptor	Malate dehydrogenase (quinone) Quinoprotein glucose dehydrogenase

1.1.99: other acceptors	Choline dehydrogenase L2HGDH

Enzymes

Activity	Active site Binding site Catalytic triad Oxyanion hole Enzyme promiscuity Catalytically perfect enzyme Coenzyme Cofactor Enzyme catalysis Enzyme kinetics Lineweaver–Burk plot Michaelis–Menten kinetics

Regulation	Allosteric regulation Cooperativity Enzyme inhibitor

Classification	EC number Enzyme superfamily Enzyme family List of enzymes

Types	EC1 Oxidoreductases(list) EC2 Transferases(list) EC3 Hydrolases(list) EC4 Lyases(list) EC5 Isomerases(list) EC6 Ligases(list)

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