Metabolism of acetoin in mammalian liver slices and extracts. Interconversion with butane-2,3-diol and biacetyl.
1. [(14)C]Acetoin was enzymically synthesized from [(14)C]pyruvate with a pyruvate decarboxylase preparation. Its optical activity was [alpha](20) (d)-78 degrees . 2. Large amounts (1000-fold higher than physiological concentrations) of acetoin were incubated with rat liver mince. Acetoin disappeared but very little (14)CO(2) was evolved. A compound accumulated, which was purified and identified as butane-2,3-diol. Chromatography on borate-impregnated paper indicated the presence of both the erythro and threo forms. 3. Liver extracts capable of interconverting biacetyl, acetoin and butane-2,3-diol were obtained. These interconversions were catalysed by two different enzymes: acetoin dehydrogenase (EC 1.1.1.5) and butane-2,3-diol dehydrogenase (EC 1.1.1.4), previously identified in bacteria. Both required NAD(+) or NADP(+) as cofactors and were different from alcohol dehydrogenase. The equilibrium in both cases favoured the more reduced compound. 4. The activity of butane-2,3-diol dehydrogenase was decreased by dialysis against EDTA: the addition of Co(2+), Cu(2+), Zn(2+) and other bivalent metal ions restored activity. 5. Biacetyl reductase was resolved into multiple forms by CM-Sephadex chromatography and electrophoresis.
D000429:Alcohol Oxidoreductases / Q000032:analysis / Q000378:metabolism; D000818:Animals; D002074:Butanones / Q000378:metabolism*; D002245:Carbon Dioxide / Q000096:biosynthesis; D002247:Carbon Isotopes; D002262:Carboxy-Lyases; D002845:Chromatography; D002854:Chromatography, Paper; D003035:Cobalt / Q000378:metabolism; D003300:Copper / Q000378:metabolism; D003956:Dialysis; D004492:Edetic Acid; D004586:Electrophoresis; D006018:Glycols / Q000378:metabolism; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000032:analysis; D008099:Liver / Q000201:enzymology / Q000378:metabolism*; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D011773:Pyruvates; D051381:Rats; D015032:Zinc / Q000378:metabolism
D002074:Butanones; D002247:Carbon Isotopes; D006018:Glycols; D007527:Isoenzymes; D011773:Pyruvates; D009243:NAD; D002245:Carbon Dioxide; D003035:Cobalt; D009249:NADP; D003300:Copper; D004492:Edetic Acid; D000429:Alcohol Oxidoreductases; D002262:Carboxy-Lyases; D015032:Zinc