Differential properties of phosphatidate phosphohydrolase and diacylglyceride lipase activities in retinal subcellular fractions and rod outer segments.
1. The effect of magnesium and dl-propranolol on phosphatidate phosphohydrolase (PAPase) and diacylglycerol lipase (DGL) activities in isolated rod outer segments (ROS) and of the former on subcellular fractions from bovine retina was investigated. 2. Mg(2+)-independent PAPase activity was found in ROS, whereas in the other subcellular fractions PAPase activities both dependent on and independent of Mg2+ were detected. 3. The membrane-bound PAPase activity was stimulated at low concentrations of Mg2+ and inhibited at higher concentrations. The soluble activity was always stimulated by the ion. 4. dl-Propranolol (1000 microM) exerted a slight stimulatory effect on PAPase in ROS whereas total PAPase activity of microsomal fraction was not affected. 5. Mg2+ (0.2 mM) stimulated DGL activity (30%) whereas it was inhibited at higher concentration. 6. DGL lipase activities, both dependent on and independent of Mg2+, were detected in subcellular fractions of bovine retina. 7. DGL properties in ROS are also described.
Pasquaré
S J
SJ
Instituto de Investigaciones Bioquimicas, Universidad Nacional del Sur, Bahía Blanca, Argentina.
Giusto
N M
NM
D000818:Animals; D002417:Cattle; D003600:Cytosol / Q000201:enzymology; D008071:Lipoprotein Lipase / Q000378:metabolism*; D008274:Magnesium / Q000494:pharmacology; D008861:Microsomes / Q000201:enzymology; D008928:Mitochondria / Q000201:enzymology; D010711:Phosphatidate Phosphatase / Q000378:metabolism*; D011433:Propranolol / Q000494:pharmacology; D012160:Retina / Q000187:drug effects / Q000201:enzymology* / Q000648:ultrastructure; D012374:Rod Cell Outer Segment / Q000201:enzymology*; D013347:Subcellular Fractions / Q000201:enzymology*; D013574:Synaptosomes / Q000201:enzymology
D011433:Propranolol; D008071:Lipoprotein Lipase; D010711:Phosphatidate Phosphatase; D008274:Magnesium