Kinetics of alpha-dicarbonyls reduction by L-glycol dehydrogenase (NAD+) from Enterobacter aerogenes

L-glycol dehydrogenase from Enterobacter aerogenes shows a high affinity by NADH (Ks = 2-4 microM; Km = 4.3-9.7 microM), which indicates that it must operate in vivo saturated with this coenzyme. Michaelis and dissociation constants for the reduction of the carbonyl substrates assayed (diacetyl, 2,3-pentanedione, methylglyoxal and ethyl pyruvate) are similar to those reported for other diacetyl reducing enzymes. The kinetic mechanism followed by these reactions has also been studied. Our results prove that the reduction of diacetyl and ethyl pyruvate takes place via an Ordered Bi-Bi system with the coenzyme as the leading substrate. Methylglyoxal and 2,3-pentanedione are reduced by the same mechanism or by a Theorell-Chance one.