Proline metabolism in Leishmania tarentolae

Abstract

Leptomonads of Leishmania tarentolae were able to grow in Trager's defined medium C deficient in glucose or l-proline, but not without both. In addition, inositol and glycine could be deleted without any adverse effect as long as either glucose or l-proline was present. Cells could grow in methionine-free media only if l-proline was present. Respiration studies indicated that l-proline, glutamate, and aspartate were the only amino acids in medium C capable of stimulating O 2 uptake by L. tarentolae. Methionine and serine appeared to inhibit respiration. d-proline and hydroxyproline could not substitute for the l form. Thin layer chromatography separation of free amino acids from cells incubated in 14C l-proline contained radioactive proline, glutamate, and alanine. Separations of tricarboxylic acid cycle acids contained a number of radioactive intermediates including α-ketoglutarate and malate as well as pyruvate. Although Δ 1-pyrroline-5-carboxylic acid could not be found in chromatograms, an increased positive O-aminobenzaldehyde reaction was found in cell extracts incubated in l-proline. The above results suggest the presence of a proline-glutamate interconversion oxidation pathway similar to the proline oxidase metabolic system found in a variety of organisms. Alanihe- 14C was found in cells incubated with 14C l-proline. Alanine is thought to be derived from pyruvate because of: (a) The presence of 14C Krebs cycle acids, (including malate) and pyruvate; (b) demonstration of an NADP dependent malic enzyme, and (c) formation of only 14C alanine by cells incubated in 14C sodium pyruvate.