γ-Glutamyltranspeptidase Activity and the Properties of the Extracellular Glutaminase from Aspergillus oryzae

抄録

The extracellular glutaminase from Aspergillus oryzae MA-27-IM was found to have γ-glutamyltranspeptidase (GGT) activity, and the properties of the enzyme as to this reaction were investigated.
Temperature, *pH and various reagents affected the GGT reaction in the same way as the glutaminase reaction. As the concentration of glycylglycine increased, the formation of γ-glutamylglycylglycine was enhanced, while the hydrolysis of glutamine was depressed. When L-γ-glutamyl-p-nitroanilide was used as a γ-glutamyl donor, the enzyme could utilize some peptides containing glycine residues at their C-termini as γ-glutamyl acceptors, but the reaction rates were lower than with glycylglycine, while free amino acids could not serve as γ-glutamyl acceptors. Further investigation suggested that the GGT reaction proceeded through a ping-pong Bi Bi mechanism.