Metabolism of acetoin in mammalian liver slices and extracts. Interconversion with butane-2,3-diol and biacetyl

Abstract

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.

Isolation and Characterization of Multiforms of Aldehyde Reductase in Chicken Kidney

“…Although the properties of the aldehyde reductases and carbonyl reductases presented here differ from those of diacetyl reductases, they reduced diacetyl rapidly. Since the existence of multiforms of diacetyl reductase in crude enzyme preparations has been reported [44], it is possible that this heterogeneity might be caused by multiforms of aldehyde reductase and carbonyl reductase. AR2 especially reduced diacetyl and acetoin with higher affinity than rat and bovine liver diacetyl reductases [44,45] and rat liver butanediol dehydrogenase [44].…”

“…Since the existence of multiforms of diacetyl reductase in crude enzyme preparations has been reported [44], it is possible that this heterogeneity might be caused by multiforms of aldehyde reductase and carbonyl reductase. AR2 especially reduced diacetyl and acetoin with higher affinity than rat and bovine liver diacetyl reductases [44,45] and rat liver butanediol dehydrogenase [44]. Thc enzyme may participate in the metabolism of diacetyl, acetoin and 2,3-butanediol in chicken kidney.…”

“…Two distinct enzymes, diacetyl reductase (EC 1 .I .1.5) and butanediol dehydrogenase (EC 1.1.1.4), responsible for the formation of acetoin, have been partially purified from the liver of rat [44], cow [45] and pigeon [46]. Although the properties of the aldehyde reductases and carbonyl reductases presented here differ from those of diacetyl reductases, they reduced diacetyl rapidly.…”

“…[43] which is further metabolized to 2,3-butanediol [44]. Two distinct enzymes, diacetyl reductase (EC 1 .I .1.5) and butanediol dehydrogenase (EC 1.1.1.4), responsible for the formation of acetoin, have been partially purified from the liver of rat [44], cow [45] and pigeon [46].…”

Scientific Opinion on Flavouring Group Evaluation 11, Revision 2 (FGE.11Rev2): Aliphatic dialcohols, diketones, and hydroxyketones from chemical groups 8 and 10

“…In liver preparations obtained from rats and rabbits, greater than 95 % of the radioactivity of 2,3-14 C-acetoin was detected as a mixture of stereoisomers of butane-2,3-diol (Gabriel et al, 1971). Although reductions of diacetyl and acetoin have been observed in animals in vivo and in animal tissue preparation in vitro at high concentrations, it appears that oxidation of diacetyl is a major endogenous metabolic pathway.…”