Formation of γ-glutamylglycyglycine by extracellular glutaminase of Aspergillus oryzae

γ-Glutamylglycylglycine (γ-GluGlyGly) was formed through the γ-glutamyltranspeptidase (GGT) reaction catalyzed by glutaminase in a water extract of wheat bran koji obtained with Aspergillus oryzae MA-27-IM. The yield of γ-GluGlyGly was about 18% from l-glutamine in a reaction mixture containing 50 mM l-glutamine, 50 mM glycylglycine, and the extract (0.1 unit ml as GGT activity) in a 100 mM Tris-HCl buffer solution (pH 7.2), which was incubated for 7 h at 30°C. The γ-GluGlyGly formed was purified by ion exchange chromatographies, and the identified by chemical and enzymatic methods as well as by infrared and PMR spectroscopic analyses.