Proline Metabolism in <i>Leishmania donovani</i> Promastigotes*

Abstract

SYNOPSIS Oxygen uptake of Leishmania donovani culture promastigotes was stimulated by L‐proline and to a lesser extent by L‐glutamate and L‐arginine. L‐proline reversed partially KCN‐induced inhibition of respiration and completely, inhibition caused by malonate. Labeled proline, glutamate, alanine, and arginine were detected by thin layer chromatography in the free amino acid pool from cells incubated with L‐proline‐ 14 C. Labeled tricarboxylic acid cycle intermediates, α‐ketoglutarate, succinate, fumarate, malate, and oxaloacetate, also were found by this method in extracts from organisms incubated with L‐proline‐ 14 C which contained also pyruvate. Cells incubated with malic acid‐ 14 C contained labeled alanine, glutamate, and arginine. Labeled L‐proline was not found in promastigotes incubated with D‐glucose‐ 14 C, although arginine, glutamate, and alanine were detected in extracts from these organisms. Indirect evidence for the presence of a NADP‐dependent malic enzyme was obtained by Ochoa's method. All results suggest the presence of a proline‐glutamate interconversion pathway in L. donovani promastigote culture forms.