Liver γ-Glutamyl Transpeptidase Activity after Cyclosporine A and Amlodipine Treatment

Abstract

γ-Glutamyl transpeptidase (GGT) (E.C.2.3.2.2) is a cell — surface enzyme that catalyzes transfer of the γ-glutamyl moiety of glutathione and other γ- glutamyl compounds to a variety of amino acids and peptides. It has also been suggested that the action of GGT may be involved in protein synthesis, amino acid transport, collagen formation and degradation of peptides (Meister, 1974; Orlowski and Meister, 1970). The GGT, a heterogenous sialoglycoprotein is localized in many mammalian tissues and cells (Kottgen et al, 1976; Tate and Meister, 1976). The pattern of GGT sugar chains can alter during development and in pathological states (Kottgen et al, 1976; Yamashita et al., 1993). The GGT activity is different in individual organs, tissues and cells and is dependent on physiological or pathological states, drugs and many others (Chung et al, 1990; Nishimura and Teschke, 1983; Paolicchi et al., 1993; Stastny et al., 1992; Weber et al., 1992). The GGT is involved in γ-glutamyl cycle and more recent studies have suggested that the enzymes of the cycle participate in a variety of essential cellular reactions and defense mechanisms (Meister, 1974).