Purification and properties of gamma-glutamyl transpeptidase from human testis

Gamma-glutamyl transpeptidase was purified to apparent homogeneity from human testis by DEAE cellulose, acetone, precipitation, fractionation by ammonium sulphate, Sephacryl S-200 chromatography, Q-Sepharose chromatography and S-Sepharose chromatography following solubilization of the enzyme by Triton X-100. The purified enzyme had an apparent molecular weight of 54 KDa by Sephacryl S-200 gel filtration. On sodium dodecyl sulphate polyacrylamide gel electrophoresis, two submits of molecular weight 38 KDa and 14 KDa were obtained. The purified enzyme showed a single band with pI 6.0. The Km value and the optimal pH of the enzyme for L-gamma-glutamyl-3-carboxy-4-nitroanilide were found 1.09 mmol/l and 8.2-8.5, respectively. Serial lectin binding study with various lectin columns showed that the majority of the asparagine-linked oligosaccharides of the enzyme was complex-types. However, complex-types with bisecting N-acetylglucosamine residue were not recognized.