CPIA-cholesterol ester formation

Finally, the enzymatic nature of CPIA-cholesterol ester formation will be briefly mentioned. None of the enzyme preparations of three known biosynthetic pathways for cholesterol esters, namely, acyl-CoA cholesterol Q-acyltransferase (ACAT), lecithin cholesterol 0-acyltransferase (LCAT), nor cholesterol esterase, was effective in producing CPIA-cholesterol ester from the Ba isomer or CPIA. In contrast, the 9,000 g supernatant or microsomal fractions from liver or kidney homogenate were found to be capable of producing CPIA-cholesterol ester without the addition of any cofactors. As substrate, only the Ba isomer was effective, and none of the 3 other fenvalerate isomers nor free CPIA was effective. The hepatic enzyme preparation also catalyzed hydrolysis of fenvalerate, and in this case all the 4 isomers were utilized as substrates. These facts imply that CPIA-cholesterol ester is formed from the Ba isomer through a transesterification reaction via intermediary acyl-enzyme complex. 

The enzyme activity responsible for CPIA-cholesterol ester formation is distributed in several tissues of animal species including rats, mice, dogs and monkeys, as shown in Table VI. No tissue enzymes were found to react with the Aa, a6 or b6 isomer. 

Table VI. CPIA-Cholesterol Ester Formation from the Btx Isomer...

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