Abstract
The interactions between phosphatidylinositol and membrane-bound enzymes in rat liver microsomes were studied by using phosphatidylinositol (PI)-specific phospholipase C of Bacillus thuringiensis and nonionic, anionic and cationic detergents. The dependence of activity of nucleoside diphosphatase on the detergent concentration varied with the detergents used. However, maximal activity with each detergent was attained within 30 min, and the enzyme activity was relatively stable during exposure to each detergent. When phosphatidylinositol in the microsomal membrane was hydrolyzed, the glucose-6-phosphatase activity was decreased in the presence of taurocholate. Nucleoside diphosphatase and 5'-nucleotidase were released by the breakdown of phosphatidylinositol in the membrane, while adenosine triphosphate (ATP) ase, reduced nicotinamide adenine dinucleotide (NADH)-cytochrome b5 reductase and carboxylesterase were not released. The pattern of release of nucleoside diphosphatase was significantly different from that of 5'-nucleotidase, and the release of the latter enzyme was greater than that of the former. Also, nucleoside diphosphatase was more extensively released from the microsomal membrane by treatment with taurocholate than with PI-specific phospholipase C, while the release of 5'-nucleotidase activity was greater on treatment with this phospholipase C than with taurocholate.
