Biochemical characteristics of a preneoplastic marker enzyme glutathione S-transferase P-form(7-7).

Investigation of biochemical characteristics of the glutathione S-transferase P-form (GST 7-7), a specific marker enzyme for preneoplastic cells arising during chemical hepatocarcinogenesis in the rat, revealed distinct functional differential from six other major GST forms. While the GST 7-7 substrate specificity was generally broader, binding ability for diverse organic anions such as bilirubin, hematin, and sulfobromophthalein was as high as in any of the other six forms. Furthermore, the enzymatic activity of GST 7-7 was found to be highly insensitive to the inhibitory actions of a wide range of organic anions at physiological pH in contrast to the other forms which proved more susceptible. The functional characteristics of GST 7-7 may in part account for its overproduction in the preneoplastic cells.