Purification and properties of gamma-glutamyltranspeptidase from Bacillus subtilis (natto).

To understand the mechanism by which gamma-polyglutamic acid (gamma-PGA) in the sticky material of natto was synthesized, we purified the gamma-glutamyltranspeptidase (gamma-GTP) (EC 2.3.2.2) from the culture broth of Bacillus subtilis (natto) to homogeneity. gamma-GTP was composed of two subunits with molecular weight of 45,000 and 22,000. The N-terminal amino acid sequence of light subunit was homologous with that of gamma-GTP from Escherichia coli. The optimum pH and temperature of activity were 8.5 and 60 degrees C. The enzyme was inactivated by incubation for 15 min at pH 8.0 and 55 degrees C, but little loss of the activity was detected at 40 degrees C. gamma-GTP used glutamine as a gamma-glutamyl donor and acceptor for gamma-PGA synthesis. Dipeptides were better gamma-glutamyl acceptors than free amino acids.