Enzymes of the Ornithine‐Arginine Metabolism of Trypanosomatids of the Genus <i>Herpetomonas</i>*

Abstract

SYNOPSIS. Five strains of trypanosomatids, Herpetomonas megaseliae, H. samuelpessoai, H. muscarum muscarum, H. muscarum ingenoplastis and a newly isolated Herpetomonas sp., were examined for the enzymes of arginine‐ornithine metabolism. Ornithine carbamoyltransferase (E.C. 2.1.3.3) and argininosuccinate lyase (E.C. 4.3.2.1) were detected in cell extracts of H. megaseliae, H. samuelpessoai and H. muscarum muscarum but not of others. Both enzymes seemed repressible by arginine, which could account for their apparent absence in H. muscarum ingenoplastis and Herpetomonas sp., which grow in a complex, arginine‐rich medium. Additionally, arginine deiminase (E.C. 3.5.3.6) and citrulline hydrolase were detected in cell extracts of the 5 strains examined. This latter enzyme, previously described only in Tetrahymena , effects the single‐step hydrolysis of citrulline into ammonia, ornithine and CO 2 . Arginase (E.C. 3.5.3.1) and urease (E.C. 3.5.1.5) were not found in any of the strains examined. Some of the physicochemical characteristics of the enzymes encountered are described.