Variant gamma-glutamyltransferases in colorectal carcinomas.

Two variants of gamma-glutamyltransferase were demonstrated in colorectal carcinomas. When compared to the enzyme in normal large bowel mucosa, one of the variants showed reduced affinity to concanavalin A and considerable charge heterogeneity largely due to variable sialic acid content. The other variant appeared to be an asialo form with no affinity to concanavalin A. The two novel forms were of identical size and antigenicity compared to the normal enzyme. They might therefore reflect different post-translational modifications of the carbohydrate moiety of the enzyme.