Enzymic esterification of cholesterol in rat intestinal mucosa catalyzed by acyl-CoA: cholesterol acyltransferase.
Previous work has shown CoA-dependent esterification of cholesterol in rat intestinal mucosa. Using (1-(14)C)oleoyl-CoA as the labeled substrate, we have proved that the esterification is catalyzed by acyl-CoA: cholesterol acyltransferase (ACAT) existing in the 'microsomal fraction' of the mucosal cell. The apparent K(m) for oleoyl-CoA is 25 microM, the optimal pH 7.4-7.9, and the optimal concentration of albumin 10-20 mg/ml. The reaction is rectilinear for only 2 min. Increasing the microsomal cholesterol concentration by incubation with plasma from patients with familial lecithin: cholesterol acyltransferase deficiency leads to increasing ACAT activity. The ACAT was inhibited by taurocholate and by the thiol-blocking agent 5,5'-dithiobis(2-nitrobenzoic acid). The specific activity of the enzyme is high-that is, approximately 1 nmol cholesteryl oleate formed x mg microsomal protein(-1) x min(-1).
Norum
K R
KR
Institute for Nutrition Research, School of Medicine, University of Oslo, Blindern, Oslo, Norway.
Helgerud
P
P
Lilljeqvist
A C
AC
D000818:Animals; D002784:Cholesterol / Q000378:metabolism*; D004951:Esterification; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000166:cytology / Q000201:enzymology*; D008297:Male; D008861:Microsomes / Q000201:enzymology; D051381:Rats; D017208:Rats, Wistar; D002785:Sterol O-Acyltransferase / Q000378:metabolism*
D002784:Cholesterol; D002785:Sterol O-Acyltransferase