Metabolism of 2-oxoaldehydes in yeasts. Possible role of glycolytic bypath as a detoxification system in l-threonine catabolism by Saccharomyces cerevisiae

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Abstract
L-Threonine catabolism by Saccharomyces cerevisiae was studied to determine the role of glycolytic bypath as a detoxyfication system of 2-oxoaldehyde (methylglyoxal) formed from l-threonine catabolism. During the growth on l-threonine as a sole source of nitrogen, a large amount of aminoacetone was accumulated in the culture. The enzymatic analyses indicated that l-threonine was converted into either acetaldehyde and glycine by threonine aldolase or 2-aminoacetoacetate by NAD-dependent threonine dehydrogenase. Glycine formed was condensed with acetyl-CoA by aminoacetone synthase to form 2-aminoacetoacetate, a labile compound spontaneously decarboxylated into aminoacetone. The enzyme activities of the glycolytic bypath of the cells grown on l-threonine were considerably higher than those of the cells grown on ammonium sulfate as a nitrogen source. The result indicated the possible role of glycolytic bypath as a detoxification system of methylglyoxal formed from l-threonine catabolism.