The preparation and chemical composition of the multiple forms of beta-glucuronidase from the female rat preputial gland

Abstract

Beta-Glucuronidase isolated from the preputial gland of the female rat has previously been shown to be a tetrameric glycoprotein. We have now separated the enzyme into several molecular forms by chromatography on hydroxylapatite columns. The three major forms (A, B, and C) have a very similar or identical amino acid composition, and kinetic and stability studies on forms B and C disclosed no differences between these two forms. However, from C contained much more carbohydrate than forms A and B, which were very similar in carbohydrate composition. The sugars in forms A and B are mannose (2.8%), glucosamine (1.9%), fucose (0.2%), galactose (0.16%), and glucose (0.17%). Form C is a little higher in mannose content, but, more distinctively, is much richer in fucose (0.6%), galactose (1.1%), and glucose (1.5%). The presence of glucose was established by paper chromatography as well as by gas-liquid chromatography, and several special experiments were performed to rule out the possibility that this hexose was present in a persistent contaminant. Direct chemical analysis for sialic acid consistently showed the absence of this sugar in the enzyme. The fact that the carbohydrate-protein linkage is alkali-stable suggests that the linkage involves an asparaginyl-N-acetylglucosamine residue. The NH2-terminal amino acid in the polypeptide chain is leucine.