The effect of diphenylamine on terminal respiration in bloodstream and culture forms of Trypanosoma brucei.

Abstract

SYNOPSIS. Diphenylamine was shown to be a potent inhibitor of cyanide insensitive respiration in both bloodstream and newly established culture forms of the same isolate of Trypanosoma brucei, with the L‐α‐glycerophosphate oxidase system having the greatest sensitivity to the inhibitor. The NADH oxidase activity of bloodstream forms was at least twice as sensitive to diphenylamine as the corresponding activity in culture forms, suggesting different routes of NADH oxidation in the 2 forms. The oxidation of L‐α‐glycerophosphate was inhibited to a similar degree in both culture and bloodstream forms. L‐α‐glycerophosphate oxidation in bloodstream forms differed from that found in culture forms in that the bloodstream system, unlike that in the culture form, was unable to donate electrons to cytochrome c. In culture form trypanosomes there was a distinct difference in the degree of diphenylamine inhibition on the oxidation of L‐α‐glycerophosphate, NADH, and succinate, suggesting the participation of separate flavoproteins in the oxidation of these substrates.