Multiple forms of human gamma-glutamyltransferase: preparation and characterization of different molecular weight...

Eight fractions of human gamma-glutamyltransferase were prepared from liver tissue, serum and bile by gel filtration. Bile, pooled serum from patients with high gamma-glutamyltransferase activities and serum in which liver tissue had been incubated, each contained an enzyme fraction with molecular weight greater than 10(6). A fraction of about 80,000 molecular weight was obtained from bile, and by incubation of liver tissue in serum or sodium chloride solution, but not from the serum pool. The main enzyme fraction in native serum had a molecular weight of about 300,000, and the molecular weight of gamma-glutamyltransferase partially purified from liver was initially 160,000. The fractions had similar Km and Ki values, and differences in heat stability and binding to concanavalin A were not marked.