Microsomal Synthesis of Di- and Triacylglycerols in Rat Liver and Ehrlich Ascites Cells

Abstract

The overall activity and specificity of the acyltransferases involved in triacylglycerol biosynthesis were compared in microsomes of normal rat liver and Ehrlich ascites cells using a variety of synthetic mono- and diacylglycerols of known structure as substrates. The ascites cell microsomes converted 2-monoacyl-sn-glycerols to diacylglycerols (25–67 nmol/h per milligram protein) at about two to three times the rate of liver microsomes (9–26 nmol/h per milligram protein). They yielded two to three times more 2,3-diacyl-sn-glycerols (15–26%) than did liver microsomes (6–12%), although the major product of acylation of the 2-monoacyl-sn-glycerol was the 1,2-isomer (73–85%). The microsomes of the ascites cells converted two to three times as much 2,3-diacyl-sn-glycerol to triacylglycerol as did liver microsomes, although both tissues acylated 1,2-diacyl-sn-glycerols preferentially (58–85%). It is suggested that the ascites cells may have reverted to a more primitive stage of lipid metabolism characterized by the ability of direct esterification of the products of lipase activity.