Inhibition of Human Aldehyde Dehydrogenase Isozymes by Propiolaldehyde

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Abstract
Propiolaldehyde–a metabolite of pargytine (Shirota et al., 1979) can function as an inhibitor or as a substrate of human aldehyde dehydrogenase (EC 1.2.1.3), dependent on conditions. In the presence of high concentration of NAD, propiolaldehyde is a substrate for both the cytoplasmic E, isozyme and the mitochondrial E2 isozyme. The K. values are comparable to those with other short chain aldehydes; the maximal velocity is also similar for E2 but lower by about threefold for E. Preincubation with propiolaldehyde in the absence of NAD produces inactivation with K values of 1.6 μM for E, and 1.8 μ for E2. NAD, but not propanal, protects both isozymes against inactivation with propiolaldehyde.