Studies of the molecular pathogenesis of hexane neuropathy. I. Evaluation of the inhibition of glyceraldehyde‐3‐phosphate dehydrogenase by 2,5‐hexanedione

Comparison of 2,5-HD and acetone with p-chloromercuribenzoate and N-ethylmaleimide demonstrated that the former are not significant sulfhydryl reagents, since they must be present at more than 10(4) times higher concentrations than PCMB or NEM to effect measurable inhibition of this enzyme.

Abstract

Inhibition of the sulfhydryl enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) by 2,5-hexanedione (2,5-HD) was found to be irreversible, proceeding via a reversible enzyme-inhibitor intermediate, while acetone was a weak reversible inhibitor. Comparison of 2,5-HD and acetone with p-chloromercuribenzoate (PCMB) and N-ethylmaleimide (NEM) demonstrated that the former are not significant sulfhydryl reagents, since they must be present at more than 10(4) times higher concentrations than PCMB or NEM to effect measurable inhibition of this enzyme. Thus it is unlikely that inhibition of GAPDH by 2,5-HD has any significance in the molecular pathogenesis of hexane neuropathy. The irreversibility of 2,5-HD inhibition, on the othe hand, suggests that 2,5-HD reacts with amino groups rather than sulfhydryl groups on proteins. This reaction is proposed as the molecular lesion in hexane neuropathy.