Substrate specificity of microsomal 1-acyl-sn-glycero-3-phosphoinositol acyltransferase in rat submandibular gland for polyunsaturated long-chain acyl-CoAs.
Microsomal 1-acyl-sn-glycero-3-phosphoinositol (1-acyl-GPI) acyltransferase in the rat submandibular gland showed the highest specific activities for eicosanoid-related polyunsaturated acyl-CoAs, such as arachidonoyl-, bishomo-gamma-linolenoyl- and 5,8,11,14,17-eicosapentaenoyl-CoAs, with low Km values. High activities were also obtained with acyl-CoAs having long (more than 14 carbon atoms) and n - 6 unsaturated (more than 3 double bonds) acyl chains. This enzyme also utilized acyl-CoAs having trans-unsaturated or branched chains, but not short-chains, as substrates, although the activity levels for trans-unsaturated acyl-CoAs were lower than those for cis-unsaturated acyl-CoAs. Chronic administration of isoproterenol induced decreases of this enzyme activity and the content of arachidonic, bishomo-gamma-linolenic and 5,8,11,14,17-eicosapentaenoic acids at the sn-2 position of phosphatidylinositol. These results suggest that enrichment of arachidonic acid in the sn-2 position of phosphatidylinositol is established by the high specificity and affinity of 1-acyl-GPI acyltransferase for arachidonoyl-CoA. On the other hand, the low level of bishomo-gamma-linolenic and 5,8,11,14,17-eicosapentaenoic acids in the sn-2 position of phosphatidylinositol may be explained by their limited availability.
Yashiro
K
K
Department of Oral Biochemistry, Asahi University School of Dentistry, Gifu, Japan.
Kameyama
Y
Y
Mizuno-Kamiya
M
M
Shin
S O
SO
Fujita
A
A
D000214:Acyl Coenzyme A / Q000737:chemistry / Q000378:metabolism*; D000217:Acyltransferases / Q000378:metabolism*; D000818:Animals; D002458:Cell Fractionation; D003902:Detergents / Q000494:pharmacology; D004228:Dithionitrobenzoic Acid / Q000378:metabolism; D015777:Eicosanoids / Q000737:chemistry / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000737:chemistry / Q000378:metabolism*; D007295:Inositol Phosphates / Q000378:metabolism*; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D008861:Microsomes / Q000201:enzymology*; D010716:Phosphatidylinositols / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013363:Submandibular Gland / Q000201:enzymology*; D013379:Substrate Specificity
D000214:Acyl Coenzyme A; D003902:Detergents; D015777:Eicosanoids; D005231:Fatty Acids, Unsaturated; D007295:Inositol Phosphates; D010716:Phosphatidylinositols; C014575:glycerylphosphoinositol; D004228:Dithionitrobenzoic Acid; D000217:Acyltransferases; C038660:1-acylglycerophosphorylinositol acyltransferase; D007545:Isoproterenol