Bovine kidney gamma-glutamyltransferase. Solubilized forms, biochemical and immunochemical properties

By digestion of detergent-solubilized gamma-glutamyltransferase (GGT), isolated from bovine kidney with bromelain, the liberation of 4 protein fragments was demonstrated. The fragment migrating most quickly in gel electrophoresis showed gamma-glutamyltranspeptidase activity and the most slowly migrating fragment showed peptidase activity. Protease-solubilized GGT is a sialoprotein with a molecular weight of 95,000. After treatment with sodium dodecylsulfate it was separated into two unequal subunits with molecular weights of 26,000 and 69,000. Sugar components were found only in the heavy subunit. Some catalytic differences were found between the two solubilized GGT forms. The immunoprecipitate obtained from detergent-solubilized GGT retained about 50% of the initial enzyme activity. The enzyme is inactivated with phenylmethanesulfonyl fluoride in the presence of maleate and with 6-diazo-5-oxo-L-norleucine.