A cytosolic flavin-containing enzyme catalyzing reduction of cytochrome c in Trypanosoma cruzi: kinetic studies with cytochrome c as substrate.

The kinetic mechanism of cytochrome c reduction by a Trypanosoma cruzi cytosolic flavoenzyme was investigated by initial velocity determinations, by product inhibition patterns, and by the characteristics of inhibition by analogs. The data suggest a two-site ping-pong mechanism in which NADPH reduces the flavin, which is then reoxidized in two one-electron steps by reaction with two molecules of cytochrome c. The two-site nature of the mechanism is probably related to the dimeric nature of the enzyme, and the binding sites of cytochrome c and NADPH are probably on opposite sites of the FAD.