Methylglyoxal and the polyol pathway. Three-carbon compounds are substrates for sheep liver sorbitol dehydrogenase.

Methylglyoxal, 1,2-propanediol and glycerol are shown to be substrates for sheep liver sorbitol dehydrogenase. With 1,2-propanediol the enzyme-catalyzed reaction occurs specifically with the R(-)-enantiomer. The maximum velocities and the specificity constants obtained for the three-carbon substrates are considerably lower than those reported previously for sorbitol, and suggest that rate-determination is imposed by catalytic steps other than the enzyme-coenzyme product dissociation. The present findings are discussed in terms of substrate specificity and stereospecificity, and may indicate novel aspects of sorbitol dehydrogenase function in relation to glucose metabolism and diabetic pathogenesis.