O₂‐Polarographic Studies on Soluble and Mitochondrial Enzymes of <i>Crithidia fasciculata</i>; Glycerophosphate Enzymes*

Abstract

SYNOPSIS. Mitochondrial and supernatant fractions were isolated from Crithidia fasciculata by grinding with neutral alumina and differential centrifugation. Supernatant fractions contained at least 2 NAD‐linked enzymes: an α‐glycerophosphate dehydrogenase and a malate dehydrogenase. The properties of these enzymes were investigated polarographically with phenazine ethosulfate acting as electron acceptor. Agaricic acid, cinnamic acid and p‐NO 2 ‐cinnamic acid were specific inhibitors of the α‐glycerophosphate dehydrogenase. Succinate, malate, DL‐α‐glycerophosphate and NADH stimulated respiration of mitochondrial preparations; O 2 uptake was greatest with succinate. KCN and antimycin A inhibited succinate respiration more than α‐glycerophosphate respiration. Amytal did not affect succinate, α‐glycerophosphate or NADH oxidation. The trypanocide suramin inhibited mitochondrial respiration at least 77% with each substrate. The relevance of these results to other members of the Trypanosomatidae is discussed.