Use of phospholipase A to compare phospholipid organization in synaptic membranes,myelin, and liposomes |
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Authors: | M. Butler L. G. Abood |
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Affiliation: | (1) Center for Brain Research and Department of Biochemistry, University of Rochester Medical Center, 14642 Rochester, New York;(2) Present address: Biological Sciences Research Center 220H, University of North Carolina, 27514 Chapel Hill, North Carolina |
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Abstract: | Summary The pattern of fatty acid release from rat synaptic membranes in the presence of phospholipase A2 (Vipera russelli) was compared to that from liposomes comprised of phospholipids. Phospholipase A2 more readily attacked myelin and synaptic membranes than liposomes prepared from total phospholipids derived from myelin. Although hydrolysis of liposomal phospholipids occurred in the absence of added calcium, the presence of 2mm CaCl2 or 2% bovine serum albumin significantly enhanced the phospholipase attack of liposomes, but not synaptic membranes or myelin. Phospholipase exhibited a marked preference for phospholipids containing docosahexaenoic acid (226) in the synaptic membranes, while with liposomes the pattern of released fatty acid reflected the fatty acid composition in the two-position of the phospholipids. Although either calcium or albumin markedly increased the phospholipase hydrolysis of liposomes, neither affected the hydrolysis of synaptic membranes or the pattern of fatty acid release from liposomes. It was concluded that the nonlipid constituents, particularly the proteins, of biomembranes were responsible for the organization of the phospholipids and accounted for the observed differences between liposomes and synaptic membranes with respect to enzymic accessibility. |
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Keywords: | phospholipase A2 phospholipid organization myelin phospholipids synaptic membrane phospholipids liposome hydrolysis phospholipase A2 cofactors |
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