Purification and comparison of several catalytic parameters of the [gamma]-glutamyltranspeptidase of rat mammary adenocarcinoma (13762) and of normal rat mammary gland

Abstract

A method for the purification of a membrane-bound glycoprotein, [gamma]-glutamyltranspeptidase (([gamma]-glutamyl)-peptide:amino-acid [gamma]-glutamyltransferase, EC 2.3.2.2), from a transplantable rat mammary tumor (13762 MT) is described. The properties of the tumor enzyme were compared with those of [gamma]-glutamyltranspeptidase similarly isolated from mammary tissue of non-pregnant multiparous rats. Evidence has been presented elsewhere that the mammary and tumor enzymes exist as groups of species differing in isoelectric point and that the tumor enzyme contains more of those species with lower isoelectric points. In this study the normal and tumor enzyme preparations are found to be identical or very similar in regards to the effect of papain on molecular size, the ratios of the enzymatic activities as measured with various amino acids, the Km for [middle dot] [gamma]-glutamyl-p-nitroanilide, and the Krmi for inhibition by glutathione. Neuraminidase treatment had no effect on these catalytic properties. The properties observed were generally similar to those previously reported for highly purified rat kidney preparations.