Multiple Forms of y - Glutamyltransferase : A Clinical Study

We have measured the amounts of different molecular forms of y-glutamyltransferase(EC 2.3.2.2), leucine aminopeptidase (EC 3.4.11.2), and alkalinephosphatase(EC 3.1.3.1) in serum of patientswithdifferenttypes of liverdisease.A highmolecular-mass (greater than 1 000 000 Da) form of yglutamyltransferaseand of each of the other enzymes is present in greatest amounts in patients with jaundice from extrahepatic obstruction. A y-glutamyltransferaseform of intermediate molecular mass (250 000 to 500 000 Da) is present in the serum from most patientswith liver disease andcan be separated by electrophoresisintoseveral bands. We found that one of these bands predominated in patients with extrahepatic obstructivejaundice, whereas the others predominated in patients with other liver diseases. Electrophoresis of serum y-glutamyltransferase may be of clinical value in distinguishing extrahepatic from intrahepatic causes of jaundice.