Further investigations on a novel gamma-glutamyl transpeptidase in human renal carcinoma.

The enzymic and immunological properties of a novel gamma-glutamyl transpeptidase found in human renal carcinoma tissues were investigated further in comparison with those of the normal kidney enzyme. On isoelectric focusing, the novel gamma-glutamyl transpeptidase separated into two main forms, having pI values below 3.6, while the normal kidney enzyme separated into multi-molecular forms with pI values of 4.0-5.0. Neuraminidase treatment diminished the difference between these two enzymes, the products of the novel enzyme and the normal kidney having pI values of 5.4 and 5.6, respectively. The percentages of the total activity of the novel gamma-glutamyl transpeptidase binding with Con A before and after neuraminidase treatment were about 40% and 80%, respectively, while the corresponding percentages of the activity of the normal kidney enzyme were less that 10% and about 25%, respectively. The novel gamma-glutamyl transpeptidase was immunologically identical with the normal kidney enzyme in the activity inhibition test and the double diffusion test. The present data suggest that the novel gamma-glutamyl transpeptidase has the same antigen site as the normal kidney enzyme, but differs from the latter at least in its sialic acid content and in some other carbohydrate moieties.