Stereospecificity of monoacylglycerol and diacylglycerol acyltransferases from rat intestine as determined by chiral phase high-performance liquid chromatography.
Using chiral phase high-performance liquid chromatography of diacylglycerols, we have redetermined the ratios of 1,2-/2,3-diacyl-sn-glycerols resulting from acylation of 2-monoacylglycerols by membrane bound and solubilized triacylglycerol synthetase of rat intestinal mucosa. With 2-oleoyl[-3H]glycerol as the acyl acceptor and oleoyl-CoA as the acyl donor, 97-98% of the diacylglycerol product was 1,2(2,3)-dioleoyl-sn-glycerol, 90% of which was the sn-1,2- and 10% the sn-2,3-enantiomer. The remaining diacylglycerol (less than 3%) was the sn-1,3-isomer. The overall yield of acylation products was 70%, of which 60% were diacylglycerols and 40% triacylglycerols. With 2-oleylglycerol ether as the acyl acceptor and [1-14C]oleoyl-CoA as the acyl donor, 90% of the diradylglycerol was 1-oleoyl-2-oleyl-sn-glycerol and 10% was the 2-oleyl-3-oleoyl-sn-glycerol. The diradylglycerols made up 96% and the triradylglycerols 4% of the radioactive product. With 1-palmitoyl-sn-glycerol as the acyl acceptor and [1-14C]oleoyl-CoA as the acyl donor, the predominant reaction product was 1-palmitoyl-3-oleoyl-sn-glycerol. The 3-palmitoyl-sn-glycerol was not a suitable acyl acceptor. Both 1,2- and 2,3-diacyl-sn-glycerols were substrates for diacylglycerol acyltransferase as neither isomer was favored when 1,2-dioleoyl-rac-[2-3H]glycerol was used as the acyl acceptor. There was a marked decrease in the acylation of the 1(3)-oleoyl-2-oleyl-sn-glycerol to the 1,3-dioleoyl-2-oleyl-sn-glycerol. It is concluded that neither monoacylglycerol nor diacylglycerol acyltransferase exhibit absolute stereospecificity for acylglycerols as fatty acid acceptors.
Lehner
R
R
Banting and Best Department of Medical Research, C.H. Best Institute, University of Toronto, Canada.
Kuksis
A
A
Itabashi
Y
Y
D000217:Acyltransferases / Q000378:metabolism*; D000818:Animals; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D051048:Diacylglycerol O-Acyltransferase; D007413:Intestinal Mucosa / Q000201:enzymology; D007421:Intestine, Small / Q000201:enzymology*; D008297:Male; D008861:Microsomes / Q000201:enzymology; D051381:Rats; D017208:Rats, Wistar; D013237:Stereoisomerism; D013379:Substrate Specificity
D000217:Acyltransferases; D051048:Diacylglycerol O-Acyltransferase; C021802:2-acylglycerol O-acyltransferase