Rapid accumulation of diacyl lipid in rat liver microsomes by selective acylation of 2-acyl-sn-glycero-3-phosphorylserine.
2-Acyl-sn-glycero-3-phosphoryl[U-14 C]serine (2-acylGPS) was prepared by digesting 1,2-dioleoyl-sn-glycero-3-phosphoryl[U-14C]serine, mixed with pig brain phosphatidylserine (PS), with Rhizopus arrhizus lipase. The labeled lysolipid was shown to be actively acylated by rat liver microsomes in the presence of acyl-CoA thioesters, with the formation of diacylPS. In experiments with unlabeled lysolipid and [14C]acyl-CoA thioesters, digestion of the products with pancreatic phospholipase A2 showed that the acyl groups had been incorporated almost exclusively at position-1. The acylation reactions were dependent on pH of the incubation medium, time of incubation, concentration of microsomal protein and of lysolipid and thioester substrates. With [14C]lysolipid there was a clear preference for long-chain saturated over unsaturated acyl group donors and highest acylation rates were recorded with stearoyl-CoA. Since stearate is the major fatty acid at position-1 of tissue PS, these findings suggest that deacylation-reacylation reactions may be of importance in regulating the fatty acid profile of this lipid. The observed rates of acylation of 2-acylGPS in vitro were high in relation to the endogenous level of PS in the microsomal membranes, and short-term incubations led to net synthesis of PS with a many-fold increase in its concentration. The question is raised whether this is a latent activity expressed under optimal assay conditions in vitro, conditions that may not obtain in a cell, or whether the high acylating potential is indicative of an important function for the addition, or turnover, of acyl groups at position-1 of the serine lipid.
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Thompson
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Belina
D000214:Acyl Coenzyme A / Q000378:metabolism; D000215:Acylation; D000818:Animals; D001923:Brain Chemistry; D005227:Fatty Acids / Q000032:analysis; D008862:Microsomes, Liver / Q000378:metabolism*; D010171:Palmitoyl Coenzyme A / Q000378:metabolism; D010718:Phosphatidylserines / Q000032:analysis / Q000378:metabolism*; D010741:Phospholipases A / Q000378:metabolism; D054467:Phospholipases A2; D051381:Rats; D013329:Structure-Activity Relationship; D013552:Swine
D000214:Acyl Coenzyme A; D005227:Fatty Acids; D010718:Phosphatidylserines; D010171:Palmitoyl Coenzyme A; C017725:stearoyl-coenzyme A; D010741:Phospholipases A; D054467:Phospholipases A2