Characterization of extracellular γ-glutamyl transpeptidase from Aspergillus nidulans

Abstract

Aspergillus nidulans γ-glutamyl transpeptidase (AnγGT, EC 2.3.2.2) was partially purified from the fermentation broth of carbon stressed cultures. Its temperature and pH optimum was 45 ºC and pH 8.0, respectively. AnγGT had little hydrolase activity. It utilized Gln, glutathione and less efficiently oxidized glutathione as γ-glutamyl donors (beside of γ-glutamyl-p-nitroanilide) and amino-acids and peptides (including Glu, Cys, Met, Gly-Gly and Cys-Gly) but not hydroxylamine as γ-glutamyl acceptors. We propose that the function of this enzyme is not to degrade, but to produce, γ-glutamyl compounds which may be related to the utilization of extracellular peptides and aminoacids in carbon stressed cultures.