title: Purification and characterization of diacetyl-reducing enzymes from Staphylococcus aureus.
abstract: A method was developed to purify diacetyl-reducing enzymes from Staphylococcus aureus. Two enzymes capable of catalysing diacetyl reduction were isolated, neither of which turned out to be a specific diacetyl reductase. One of them is a lactate dehydrogenase similar to the one from Staphylococcus epidermidis, which accepts diacetyl, although poorly. The other one uses as coenzyme beta-NAD and reduces uncharged alpha-dicarbonyls with more than three carbon atoms (especially the alpha-diketones diacetyl and pentane-2,3-dione), producing the L(+) form of the corresponding alpha-hydroxycarbonyls. This enzyme has an Mr of 68,000 and is, most probably, a monomer. Its optimum pH is 6.0. Its shows a high affinity for NADH and a rather low one for diacetyl, which, at least in vitro, does not seem to be as good a substrate as pentane-2,3-dione. We propose for it the systematic name L-alpha-hydroxyketone:NAD+ oxidoreductase and the recommended name of alpha-diketone reductase (NAD). We also suggest that the diacetyl reductase entry in the I.U.B. classification be suppressed.
mesh_terms: D000094:Acetoin Dehydrogenase / Q000302:isolation & purification / Q000378:metabolism*; D000429:Alcohol Oxidoreductases / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism*; D007770:L-Lactate Dehydrogenase / Q000302:isolation & purification; D009243:NAD / Q000378:metabolism; D013211:Staphylococcus aureus / Q000201:enzymology*; D013379:Substrate Specificity; D009626:Terminology as Topic
chemical_list: D007527:Isoenzymes; D009243:NAD; D000429:Alcohol Oxidoreductases; D000094:Acetoin Dehydrogenase; D007770:L-Lactate Dehydrogenase