Improved catalytic efficiency of a monomeric γ-glutamyl transpeptidase from Bacillus licheniformis in presence of subtilisin

Monomeric 30 kDa gamma-glutamyl transpeptidase (GGT(30)) was purified from culture broth of Bacillus licheniformis ER-15 along with a heterodimeric 67 kDa GGT (GGT(67)). In presence of subtilisin, GGT(30) had improved catalytic efficiency (V-max/K-m) of 59 min(-1), altered pH and temperature optima of pH 11 and 70A degrees C.and had salt-tolerant glutaminase activity. Glutaminase activity was retained even in protease-inhibited condition in presence of 2 mM PMSF. GGT(30) and subtilisin complexation was also confirmed by relative electrophoretic mobility and fluorescence quenching experiment.