DETERMINATION OF LECITHIN - CHOLESTEROL ACYLTRANSFER IN MOUSE PLASMA AND THE INFLUENCE OF MERCAPTOETHANOL AND SULFHYDRYL BLOCKING-AGENTS ON ITS ACTIVITY

1. 1. The cholesterol esterifying activity in mouse plasma has been identified as lecithin:cholesterol acyltransferase (LCAT) on the basis of stoichiometric data, predominant transfer of polyunsaturated fatty acids, wide pH optimum and inhibition of esterification by phospholipase A2 and sulphydryl blocking agents. The esterifying activity differed from that present in plasma of man, rat and other species since it was partially inhibited by mercaptoethanol and other thiols. 2. 2. Stoichiometric correlations between unesterified cholesterol, lecithin and lysolecithin were not exact, suggesting possible involvement of other enzymes in the overall esterification process during in vitro incubation of mouse plasma. 3. 3. The initial rate of cholesterol esterification was determined by in vitro incubation of mouse plasma, whose cholesterol had been labelled by prior in vivo injection of 3H-mevalonic acid. The mean rate was 281 ± 74 nmol/ml/hr (mean ± S.D., n = 12) and correlated with unesterified cholesterol concentration (r = 0.73, P < 0.01). © 1979.