Rapid Purification and Characterization of γ-Glutamyl-Transpeptidase from Shiitake Mushroom (Lentinus Edodes)

摘要

γ-Glutamyl-transpeptidase (GGT) is one of the important enzymes in the pathway of odor formation in shiitake mushroom (Lentinus edodes). Rapid purification and characterization of GGT from shiitake mushroom were studied in this work. The GGT was purified 179-fold after 3 primary steps: precipitation by ammonium sulfate, isolation by Phenyl Sepharose 6 FF, and desalting by Sephadex G-25. The enzyme, consisting of a small and a large subunit with Mr 28 KDa and 60 KDa, respectively, is composed of 17 kinds of amino acids with the ratio of basic and acidic residues 1:1.84, and its secondary structure was also determined by Fourier transform infrared spectroscopy. The properties of GGT were studied with γ-glutamyl-p-nitroanilide as the substrate. The results showed Km value of 2.601 μM, optimal temperature of 40 ℃, and isoelectric point of 6.4. In addition, the activity of GGT was promoted by Na~+, K~+, and Ca~(2+) and inhibited by Cu~(2+), Ag~+, Zn~(2+), and Fe~(3+).