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Digestion of phosphatidylcholines, absorption, and esterification of lipolytic products by Aeshna cyanea larvae as studied in vivo and in vitro
Author(s) -
Weiher Birgit,
Komnick Hans
Publication year - 1997
Publication title -
archives of insect biochemistry and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.576
H-Index - 66
eISSN - 1520-6327
pISSN - 0739-4462
DOI - 10.1002/(sici)1520-6327(1997)36:4<273::aid-arch3>3.0.co;2-t
Subject(s) - phosphatidylcholine , biochemistry , monoacylglycerol lipase , choline , lysophosphatidylcholine , phospholipid , lipase , biology , phospholipase c , chromatography , chemistry , enzyme , endocannabinoid system , receptor , membrane
Digestion and absorption of phosphatidylcholine by Aeshna cyanea larvae were studied in vivo and in vitro with the isolated digestive juice and isolated midgut. The experiments were performed with stable ether analogues (1‐alkyl‐2‐acyl‐,1,2‐dialkyl phosphatidylcholine, and 1‐monoalkyl‐lysophosphati‐dylcholine), with radioactive 1,2‐diacylphosphatidylcholine alternatively labelled in the acyl‐ and choline moieties, and with several phosphatidylcholine derivatives (1‐[1‐ 14 C]acyl‐ and 1‐[ 3 H] alkyl‐lysophosphatidylcholine, [1‐ 14 C]oleic acid, [2‐ 14 C]glycerol, phosphoryl[methyl‐ 14 C]choline, and [methyl‐ 14 C]choline). Chromatographic analyses of the digestion products revealed that phosphatidylcholine was degraded via two interconnected hydrolytic pathways involving phospholipase C, phospholipase A 2 , lipase, and alkaline phosphatase. Complete hydrolysis by these pathways yielded the same four end products: free fatty acid, glycerol, choline, and P i , which were absorbed by the midgut enterocytes. Of the intermediate hydrolysates, lysophosphatidylcholine, monoacylglycerol, and possibly phosphorylcholine were also absorbed. Radiolabelled oleic acid, glycerol, lysophosphatidylcholine and monoacylglycerol (as judged from monoalkylglycerol absorption) were incorporated into phospholipids and acylglycerols of the midgut enterocytes and were released into the haemolymph primarily in the form of diacylglycerols. In the case of glycerol ingestion, a small fraction of haemolymph radioactivity was associated with free glycerol and glycerolphosphate. After absorption by the enterocytes, radiolabelled choline was partly oxidized to betaine, partly phosphorylated, and partly incorporated into lyso‐ and phosphatidylcholine. It was recovered from the haemolymph predominantly as free choline, phosphorylcholine, and betaine. Arch. Insect Biochem. Physiol. 36:273–293, 1997. © 1997 Wiley‐Liss, Inc.