Year-end Sale % OFF 
Abstract
Acyl-CoA:1-acylglycerophosphate acyltransferase activity was found in porcine erythrocyte membranes. However, the membrane preparations did not catalyze the acylation of either 2-acylglycerophosphate or 2-acylglycerophosphocholine. The 1-acylglycerophosphate acyltransferase and the known acyl-CoA:1-acylglycerophosphocholine acyltransferase systems differ in their specificities for acyl-CoAs and in their stabilities to detergents. Diacylglycerol lipase and monoacylglycerol lipase activities were also detected in porcine erythrocytes. These two activities appear to be catalyzed by different enzymes inasmuch as diacylglycerol lipase but not monoacylglycerol lipase was completely inhibited by divalent cations. The diacylglycerol lipase was relatively specific for the 1-position yielding 2-acylglycerol. The monoacylglycerol lipase hydrolyzed 1-acylglycerol and 2-acylglycerol at comparable rates. Phosphatidic acid was dephosphorylated to form 1,2-diacylglycerol but the acyl groups of phosphatidate were not hydrolyzed significantly by the erythrocyte membranes. Thus, the origin of 1-acylglycerophosphate, a substrate for the newly described enzyme, acyl-CoA:1-acylglycerophosphate acyltransferase, in mature erythrocyte could not be ascribed to action of diacylglycerol lipase, glycerophosphate acyltransferase, or phosphatidate-specific phospholipase A. 1-Acylglycerophosphate may be supplied extracellularly or the 1-acylglycerophosphate acyltransferase activity in erythrocytes may be a remnant of de novo phosphatidate synthesizing system of reticulocytes.
Highlights
Acyl-CoA:l-acylglycerophosphate acyltransferase activity was found in porcine erythrocyte membranes
We report some apparent and the phospholipid de novo synthetic pathway, properties of 1-acyl-GPacyltransferase,diacylglycerol ligenerally localized inthe mitochondrial and microsomal pase, and monoacylglycerol lipase inporcine erythrocyte fractions of other typesofcells,does not exist[1,2,3]. membranes emphasizingtheir positional specificities
Erythrocyte membrane phospholipidsare renewed mainly by exchange with plasma phospholipids [4,5,6,7] and acylation of lysophospholipidson the cytoplasmic side ofthe membrane [8,9,10,11,12,13]. Because of their relative simplicity, mature erythrocytes provide a useful system for exam
Summary
Radiolabeled acyl-CoAs, unlabeled acyl-CoAasn,d isomers of monoacyl-GPC wereprepared as described elsewhere [31]. 1,2-Dioleoylglycerol,' l-oleoylglycerol,' and 2-oleoylglycerol were separated on 0.4 M boric acid-Silica Gel G thin-layer chromatoplates developed in chloroform-acetone-methanol 95:5:2 (v/v/v). These glycerides wereextracted, dissolved in methanol, and the concentration of each solution was determined by gas-liquid chromatography with margaric acid as an internal standard. The membrane fraction obtained by centrifugation at 20,000 g for 30 min was washed three times with 0.109 M sodium phosphate(pH 7.4). The resulting pellets were suspended inthe same buffer, frozen in liquid nitrogen, and stored at -80°C Another kind of membrane preparation was obtained as follows. Products extracted according to the method of Bligh and Dyer [37] were separated on 0.4 M boric acid-Silica Gel G thin-layer plates developedin chloroform-methanol-acetone 95:1:5 (v/v/v). Phosphorus and protein were determined by the methods of Eibl and Lands [38] and Lowry et al [39],respectively
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
