The molecular forms of gamma-glutamyl transferase in bile and serum of icteric rats.
Alterations in the molecular form of gamma-glutamyl transferase (5-glutamyl)-peptide:amino-acid 5-glutamyltransferase, EC 2.3.2.2.) were studied in the bile and serum of rats under surgical ligation of the bile duct. Polyacrylamide gel electrophoresis of the bile, followed by the enzyme stain, revealed a major, slowly migrating broad band and a minor, faster migrating band. The former was converted to the latter upon limited proteolysis of the bile with a very small amount of papain. This conversion was accompanied by a decrease in molecular size of the enzyme. Both enzyme forms were specifically adsorbed to a concanavalin A-Sepharose column. Most of the papain-treated enzyme preparation could be eluted from the column by alpha-methyl-D-glucoside, a haptenic sugar of this lectin. On the other hand, the predominant form of the enzyme in the untreated bile was eluted only in the presence both of the sugar and Triton X-100. Based on the chromatographic behavior of the two enzyme forms (detergent-solubilized and protease-solubilized form) purified from rat renal brush border membrane on concanavalin A-Sepharose column, it was concluded that the predominant form of the enzyme in the bile was the detergent-solubilized form and that the minor component represents the protease-solubilized enzyme. The serum from icteric rats was also found to contain both types of the enzyme. However, the relative amount of the protease-solubilized form to the detergent-solubilized form in the serum was much greater than that in the bile. These findings suggested that gamma-glutamyl transferase in the hepatobiliary membrane systems was solubilized into the bile mainly as the detergent-solubilized form, and that, during the process of translocation into the blood circulation, the enzyme was partly converted to the protease-solubilized form by some protease-like action.
D000818:Animals; D001646:Bile / Q000201:enzymology*; D002850:Chromatography, Gel; D007565:Jaundice / Q000201:enzymology*; D007668:Kidney / Q000201:enzymology*; D008297:Male; D010206:Papain; D011092:Polyethylene Glycols; D051381:Rats; D012995:Solubility; D005723:gamma-Glutamyltransferase / Q000032:analysis* / Q000097:blood
D011092:Polyethylene Glycols; D005723:gamma-Glutamyltransferase; D010206:Papain