Improved procedure for measuring gamma-glutamyltransferase isoenzymes in serum

In this electrophoretic procedure for measuring isoenzymes of gamma-glutamyltransferase, patterns obtained are highly reproducible and the analytical imprecision (CV) ranges from 1.10% to 6.17%. A cellulose acetate support is used, at 220 V for 40 min. Sharply resolved isoenzyme bands were made visible by fluorescence scattered light, formed by use of a coumarin derivative as donor substrate. Two bands were observed for sera from normal subjects; four bands were variably present in sera from patients with different hepatobiliary diseases. Detection of the latter was satisfactory, down to a total activity in serum of 8-10 U/L. Three of the pathological bands were associated with low- and (or) very-low-density lipoproteins, whereas a major fraction of one of the normal bands in cirrhotic sera precipitated with high-density lipoprotein. The bands in normal sera, and one of the abnormal bands, did not.