Chiral 1,2-diacylglycerols in the haemolymph of the locust, Locusta migratoria

Abstract

SummaryA 'H-NMR method using chiral shift reagents was applied in the stereochemical analysis of the haemolymph 1,2-diacylglycerols of Locusta migratoria. Conversion of the 1,2diacylglycerols into 1,2-diacetyl-3-tritylglycerols allowed the accurate determination of the enantiomeric purity, whereas direct trimethylsilylation of the unmodified or hydrogenated haemolymph 1,2-diacylglycerols proved to be less suitable because of signal broadening.In the haemolymph of Locusta, sn-1,2-diacylglycerols with a remarkably high optical purity were found to be present. In the resting locust, at least 96% of the haemolymph 1,2diacylglycerols have the sn-1,2-configuration; in locusts in which the haemolymph diacylglycerol concentration was elevated by fat body triacylglycerol mobilization induced by flight activity or injection of adipokinetic hormone, over 97% of the 1,2diacylglycerols is the sn-1,2-enantiomer. The few percent sn-2,3-enantiomer may not have been present initially.Positional distribution of the fatty acids in the fat body triacylglycerols and in the haemolymph sn-1,2-diacylglycerols obtained from locusts after a 2 h flight revealed nearly identical occupation of the sn-2-positions in both acylglycerols. The distribution patterns in the sn-l-position of the 1,2-diacylglycerols and the combined sn-1 and sn-3 positions of the triacylglycerols are compatible with the possible existence of a stereospecific sn-3-triacylglycerol lipase .

Multifaceted biological insights from a draft genome sequence of the tobacco hornworm moth, Manduca sexta

“…The transport of fatty acids (FA) in the form of diacylglycerol (DG) is a salient feature of most insects. The production and secretion of large quantities of DG by the fat body and midgut and the resulting large concentration of sn-1,2-diacylglycerol in hemolymph (Lok and van der Horst, 1980) represent a clear difference in the metabolism of lipids and the mechanisms of FA mobilization and transport between insects and vertebrates. The main insect lipoprotein, lipophorin, is the carrier of the secreted DG (Beenakkers et al, 1985).…”

Hemolymph lipids and flight activity in Helicoverpa zea (Boddie) (lepidoptera: Noctuidae)

“…Mobilization of these stored fat body reserves involves conversion to sn-1,2-diacylglycerides which are then transported to the flight muscle through the hernolymph as a DG-lipoprotein complex [7,8].…”

Insect flight muscle metabolism

“…Concerning the structure of the haemolymph DG, Tietz et al (1975) showed that 1,2-DG are released from locust fat body. These 1,2-DG are stereospecific, revealing the sn-1,2 configuration with a remarkably high purity (Tietz and Weintraub, 1980;Lok and Van der Horst, 1980). The former authors analysed fat body and haemolymph 1,2-DG of locusts at rest, using enantioselective enzymatic degradations, whereas the latter authors applied a ~H-NMR method using chiral shift reagents after chemical modification of the haemolymph 1,2-DG obtained from locusts at rest and after flight, evidencing stereospecificity of the processes involved in the production of these DG in the fat body.…”

“…Tietz et al (1975) showed that fat body microsomal acyltransferase specifically used 2-MG; moreover, the enzyme was stereospecific and preferentially synthesized sn-l,2-DG (Tietz and Weintraub, 1980). Lok and Van der Horst (1980) studied the positional distribution of the fatty acids of Locusta fat body TG and haemolymph sn-l,2-DG; the minor difference between the sn-1 position of the DG and the primary positions of the TG are compatible with the 2-MG pathway, although direct production of sn-l,2-DG by a stereospecific lipase cannot be ruled out either. Incubation experiments with the fat body lipase system and optically active TG labelled at the primary positions of glycerol could perhaps distinguish more conclusively between the possibilities.…”