Studies on the multiple forms of gamma-glutamyltransferase.

In sera of 53 patients with highly raised gamma-glutamyltransferase (gamma-GT) (EC 2.3.2.2) activity, the gamma-GT was separated by column chromatography on Sephadex DEAE A-50 into two fractions. In 35 sera only one gamma-GT fraction was found at a conductivity of 2.0--2.5 mS and in 18 sera two gamma-GT fractions were found at a conductivity of 0.2 mS and again at 2.0--2.5 mS. There was no opvious correlation to the underlying disease. In 20 sera the additional parameters, protein, protein electrophoresis, free and esterified cholesterol, bilirubin, triglycerides, lipoprotein pattern and lipoprotein X were examined. We recognized, that the two forms of the gamma-GT are not true isoenzymes but that the separation of the gamma-GT into two fractions is caused by a different distribution of the cholesterol containing lipoprotei,s.