Hydrophilic form of gamma-glutamyltransferase: proteolytic formation in liver homogenates and its estimation in serum.

By incubating liver homogenates at pH 7.0 a proteolytic modification of gamma-glutamyltransferase was demonstrated. The amphiphilic, membrane-bound enzyme was converted to a hydrophilic form whose size and electrophoretic mobility were identical to those of the hydrophilic form present in human serum. The relative amounts of the hydrophilic and the amphiphilic gamma-glutamyltransferase in various pathological sera were analyzed. In the majority of these sera the hydrophilic form constituted less than 15-20% of the total activity. High amounts (30-55%) were demonstrated in serum samples from two patients with necrosis of the liver. However, the determination of this form of gamma-glutamyltransferase appears to have little clinical significance.