Inhibition of succinic dehydrogenase by methylglyoxal.

The reaction of the carbonyl group of methylglyoxal with -SH radicals of thiols has been the subject of numerous investigations (l-9). The reactivity of the keto aldehyde with -SH compounds suggested that a similar type of reaction may occur between methylglyoxal and -SH proteins. The physiological r&e of methylglyoxal as an inhibitor of -SK enzymes is of particular interest, since this keto aldehyde may be formed during carbohydrate metabolism (10-12). Mann and Quastel (13) have reported that other aldehydes have an inhibitory effect on brain metabolism. In this paper experiments are described which demonstrate that methylglyoxal can inhibit cell metabolism. The conditions of the inhibition and its possible significance in tissue metabolism are also discussed.