On the existence of variant forms of gamma-glutamyl transferase in regenerating and neoplastic liver.

We attempted to identify variants of gamma-glutamyl transferase (GGT) which may differ in their affinity for Concanavalin A (Con A) in extracts of fetal, regenerating, neoplastic and normal adult rat liver. GGT activity was low in normal liver and did not increase after partial hepatectomy. Feeding a choline-deficient diet containing 0.05% ethionine caused a large increase in hepatic GGT activity which persisted throughout the feeding period of 23 weeks. Practically all of the GGT contained in extracts prepared with Triton X-100 from fetal, regenerating, pre-neoplastic and neoplastic rat liver as well as that from normal adult liver bound to Con A-Sepharose and was eluted from the columns with methyl-alpha-D-mannopyranoside. In contrast, GGT from bovine kidney extracts prepared in an identical way did not bind to Con A-Sepharose. We conclude that if variants of rat liver GGT exist, they cannot be reliable separated by simple affinity chromatography on Con A-Sepharose of Agarose columns.