Phosphatidylinositol-4,5-bisphosphate phospholipase C in bovine rod outer segments.
Preparations of rod outer segments from cattle retinas contained soluble and particulate phospholipase C activities which hydrolyzed phosphatidylinositol 4,5-bisphosphate (PIP2) and the other phosphoinositides. Ca2+ was required for PIP2 hydrolysis, but high (greater than 300 microM) concentrations were inhibitory. Mg2+ and spermine at low concentrations stimulated the particulate activity but inhibited the soluble. Mn2+ inhibited both. High (greater than 100 microM) concentrations of the nonhydrolyzable GTP analogue guanylyl beta,gamma-methylenediphosphonate inhibited PIP2 hydrolysis by both the soluble and particulate activities, but guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S), fluoride, and cholera and pertussis toxins were without effect. Overall phospholipase C activity in ROS was unaffected by light. Evidence was found for multiple forms of the enzyme, requiring isolation and separate characterization before ruling out regulation by light or G-protein.
Gehm
B D
BD
Department of Biochemistry, Michigan State University, East Lansing 48824.
Mc Connell
D G
DG
D000818:Animals; D002417:Cattle; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008670:Metals / Q000494:pharmacology; D009711:Nucleotides / Q000494:pharmacology; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols / Q000378:metabolism; D010786:Photoreceptor Cells / Q000378:metabolism*; D012374:Rod Cell Outer Segment / Q000378:metabolism*; D012995:Solubility; D013096:Spermine / Q000494:pharmacology; D013379:Substrate Specificity; D010738:Type C Phospholipases / Q000378:metabolism*
D008670:Metals; D009711:Nucleotides; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols; D013096:Spermine; D010738:Type C Phospholipases