Phosphatidyl inositol 4,5-bisphosphate-specific phospholipase C in bovine rod outer segment membranes.
Polyphosphoinositide-specific phosphodiesterase (phospholipase C) activity against phosphatidylinositol 4,5-bisphosphate has been examined in disrupted bovine retinal rod outer segments. The enzyme was strictly modulated by free calcium ion concentration and maximally activated at 10(-5) M Ca2+ (91 +/- 4 nmoles phosphatidylinositol 4,5-bisphosphate hydrolyzed/min/mg of protein). Guanine nucleotides did not affect in vitro phospholipase C activity either in the presence or absence of light, carbachol or epinephrine. The pH optimum at 10(-5) M Ca2+ in the presence of sodium deoxycholate was 6.5. The enzyme of bovine rod outer segments was concluded to be indirectly regulated by the phototransduction events.
Panfoli
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I
Istituto Policattedra di Chimica Biologica, Università di Genova.
Morelli
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A
Pepe
I M
IM
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002217:Carbachol / Q000494:pharmacology; D002417:Cattle; D004837:Epinephrine / Q000494:pharmacology; D006150:Guanine Nucleotides / Q000494:pharmacology; D006868:Hydrolysis; D008027:Light; D008566:Membranes / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D012374:Rod Cell Outer Segment / Q000201:enzymology*; D013379:Substrate Specificity; D010738:Type C Phospholipases / Q000378:metabolism*
D006150:Guanine Nucleotides; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates; D002217:Carbachol; D010738:Type C Phospholipases; D002118:Calcium; D004837:Epinephrine