title: The gamma-glutamyltranspeptidase of Trypanosoma cruzi.
abstract: Trypanosoma cruzi epimastigotes show gamma-glutamyltranspeptidase activity which has characteristics significantly different than the mammalian enzyme. The protozoan enzyme is localized in the cytosolic fraction, it has a Km of 1.6 mM and a Vmax of 17.4 nmol/min/mg protein with L-gamma-glutamyl-p-nitroanilide as gamma-glutamyl donor, and an optimun pH range from 7.5 to 8.0. 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. The enzyme was very sensitive to inhibition by 6-diazo-5-oxo-L-norleucine (k2 = 4.0 X 10(5)/M per min) and O-diazo-acetyl-L-serine (k2 = 1.1 X 10(4)/M per min). Phenobarbital (k2 = 8.38/M per min) and L-serine borate (Ki = 34 mM) were poor inhibitors. 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.
mesh_terms: D014355:Chagas Disease / Q000209:etiology; D003594:Cytoplasmic Granules / Q000201:enzymology; D003600:Cytosol / Q000201:enzymology; D004795:Enzyme Stability; D005978:Glutathione / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D013379:Substrate Specificity; D014349:Trypanosoma cruzi / Q000201:enzymology*; D005723:gamma-Glutamyltransferase / Q000037:antagonists & inhibitors / Q000302:isolation & purification*
chemical_list: D005723:gamma-Glutamyltransferase; D005978:Glutathione