title: Substrate specificities of the membrane-bound and partially purified microsomal acyl-CoA:1-acylglycerol-3-phosphate acyltransferase from etiolated shoots of Pisum sativum (L.).
abstract: Membrane fractions enriched in rough endoplasmic reticulum and not contaminated with plastidial membranes were isolated from etiolated shoots of Pisum sativum (L.). From these fractions the acyl-CoA:1-acyl-sn-glycerol-3-phosphate acyltransferase (EC 2.3.1.51) was solubilized by extracting the membranes with the zwitterionic detergent 3-[(3-cholamidopropyl)-dimethyl-ammonio]-1-propanesulfonate at high ionic strength. The subsequent separation of the solubilized fractions on a Mono Q column resulted in a tenfold enriched enzymic activity, which could be stabilized by polyethyleneglycol precipitation. A comparison of the substrate specificities and selectivities of the solubilized, enriched 1-acylglycerol-3-phosphate acyltransferase and the corresponding membrane-bound activity revealed no appreciable difference. Both enzymic forms specifically utilized acyl-CoA thioesters as acyl donors whereas the corresponding acyl-acyl carrier protein thioesters were not used. Furthermore, the membrane-bound as well as the solubilized enriched form showed not only higher activities with 1-oleoylthan with 1-palmitoylglycerol-3-phosphate but also pronounced specificities and selectivities for unsaturated C18-CoA thioesters. Hence, the extraplastidial 1-acylglycerol-3-phosphate acyltransferase which catalyses the formation of phosphatidic acid with an eukaryotic fatty-acid pattern was partially purified.
authors.affiliation: Institut für Allgemeine Botanik, Universität Hamburg, Ohnhorststrasse 18, 52, Hamburg, Federal Republic of Germany.
authors.forename: W
authors.initials: W
authors.lastname: Hares
authors.forename: M
authors.initials: M
authors.lastname: Frentzen