Evidence for the presence of diacylglycerol kinase in rat brain myelin |
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Authors: | David W Kahn Pierre Morell |
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Institution: | (1) Biological Sciences Research Center, Curriculum in Neurobiology, and Department of Biochemistry and Nutrition, University of North Carolina, 27599-7250 Chapel Hill, North Carolina |
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Abstract: | The previous demonstration that incubation of brain slices with 32P]phosphate brings about rapid tabeling of phosphatidic acid in myelin suggests that the enzyme involved should be present in this specialized membrane. DAG kinase (ATP:1,2-diacyglycerol 3-phosphotransferase, E.C. 2.7.1.107) is present in rat brain homogenate at a specific activity of 2.5 nmol phosphatidic acid formed/min/mg protein, while highly purified myelin had a much lower specific activity (0.29 nmol/min/mg protein). Nevertheless, the enzyme appears to be intrinsic to this membrane since it can not be removed by washing with a variety of detergents or chelating agents, and it could not be accounted for as contamination by another subcellular fraction. Production of endogenous, membrane-associated, diacylglycerol (DAG) by PLC (phospholipase C) treatment brought about translocation from soluble to particulate fractions, including myelin. Another level of control of activity involves inactivation by phosphorylation; a 10 min incubation of brain homogenate with ATP resulted in a large decrease in DAG kinase activity in soluble, particulate and myelin fractions. |
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Keywords: | Myelin diacylglycerol kinase phosphatidic acid translocation phosphoinositide phosphatidylinositol |
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