title: Diacylglycerol lipase and kinase activities in rabbit aorta and coronary microvessels.
abstract: Diacylglycerol lipase and kinase activities were measured in particulate and soluble fractions from rabbit aorta (intima-media) and coronary microvessels. With rabbit aorta, the hydrolysis at the sn-1 position of 1-palmitoyl-2-oleoyl-sn-glycerol had a pH optimum of 5-6 and was greater than hydrolysis at the sn-2 position (pH optimum of 6.5). Only the 2-monoacylglycerol accumulated during incubations at pH 5 and 6.5. These results are consistent with an ordered two-step reaction sequence where the fatty acid at the sn-1 position is released first, followed by the hydrolysis of the fatty acid from the 2-monoacylglycerol by a monoacylglycerol lipase with a neutral pH optimum. Lipase activity (sn-2 hydrolysis) at pH 6.5 was greater than kinase activity at all substrate concentrations. The presence of arachidonate at the sn-2 position of the diacylglycerol increased kinase activity but had little effect on lipase activity. Kinase activity was mainly particulate, whereas 50-60% of diacylglycerol lipase and 50% of monoacylglycerol lipase activity were soluble. Diacylglycerol lipase and kinase were also present in coronary microvessel preparations. Diacylglycerol lipase (sn-2 hydrolysis) activity in coronary microvessels was not enhanced by preincubation of the enzyme preparation with cAMP-dependent protein kinase.
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000201:enzymology*; D003331:Coronary Vessels / Q000201:enzymology*; D019852:Diacylglycerol Kinase; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008071:Lipoprotein Lipase / Q000378:metabolism*; D008833:Microcirculation / Q000201:enzymology; D010770:Phosphotransferases / Q000378:metabolism*; D011817:Rabbits; D013379:Substrate Specificity
chemical_list: D010770:Phosphotransferases; D019852:Diacylglycerol Kinase; D008071:Lipoprotein Lipase