The γ-glutamyltranspeptidase of Trypanosoma cruzi

Abstract

1. 1. Trypanosoma cruzi epimastigotes show γ-glutamyltranspeptidase activity which has characteristics significantly different than the mammalian enzyme. 2. 2. The protozoan enzyme is localized in the cytosolic fraction, it has a K m of 1.6 mM and a V max of 17.4 nmol/min/mg protein with l-γ- glutamyl-p- nitroanilide as γ-glutamyl donor, and an optimun pH range from 7.5 to 8.0. 3. 3. The best amino acid acceptors were l-histidine, l-asparagine, l-aspartate, l-glutamate and l-proline, but l-glutamine was a very poor acceptor. 4. 4. The enzyme was very sensitive to inhibition by 6-diazo-5-oxo- l-norleucine ( k 2 = 4.0 × 10 5 M per min) and O- diazo-acetyl- l- serine ( k 2 = 1.1 × 10 4 M per min ). Phenobarbital ( k 2 = 8.38 M per min ) and l-serine borate ( K i = 34 mM) were poor inhibitors. 5. 5. The activity of the enzyme was not correlated with the logarithmic phase of growth of the parasites and steadily decreases with the age of the cultures.