Evidence for a lecithin-retinol acyltransferase activity in the rat small intestine

J Biol Chem. 1988 Sep 5;263(25):12478-82.

Abstract

Cellular retinol-binding protein, type II (CRBP (II] is an abundant protein of the mature enterocytes of the small intestine. It has been shown to direct retinol to an acyl-CoA-independent esterifying activity that utilizes an endogenous acyl donor (Ong, D.E., Kakkad, B., and MacDonald, P.N. (1987) J. Biol. Chem. 262, 2729-2736). Here we report that this activity in intestinal microsomes will catalyze the transfer of acyl moieties from exogenous phosphatidylcholine (PC) to retinol-CRBP(II) to produce retinyl esters. The microsomal activity displayed positional selectivity as only the sn-1-acyl moiety of PC was transferred to retinol-CRBP(II). The retinyl ester synthase was selective for PC substrates as acyl transfer from phosphatidylethanolamine, phosphatidic acid, or free fatty acid to retinol-CRBP(II) was not observed. Some formation of retinyl esters was observed with exogenous acyl-CoA, but the amount produced was considerably lower than ester formation from exogenous PC and could be shown to be due to a different enzyme activity. Inhibitor studies clearly distinguished between the enzyme activities responsible for the acyl-CoA-dependent esterification and the phosphatidylcholine-dependent esterification of retinol. The results provide strong evidence that retinol-CRBP(II) esterification in the intestine proceeds via a phosphatidylcholine-dependent transacylase mechanism similar to that established for the esterification of cholesterol by lecithin-cholesterol acyltransferase.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acyl Coenzyme A / metabolism
  • Acyltransferases / metabolism*
  • Animals
  • Esterification
  • Intestine, Small / enzymology*
  • Lipid Metabolism
  • Male
  • Microsomes / enzymology
  • Phosphatidylcholines / metabolism
  • Phosphatidylcholines / pharmacology
  • Rats
  • Retinol O-Fatty-Acyltransferase
  • Retinol-Binding Proteins / metabolism
  • Retinol-Binding Proteins, Cellular
  • Substrate Specificity
  • Vitamin A / metabolism

Substances

  • Acyl Coenzyme A
  • Phosphatidylcholines
  • Rbp2 protein, rat
  • Retinol-Binding Proteins
  • Retinol-Binding Proteins, Cellular
  • Vitamin A
  • Acyltransferases
  • lecithin-retinol acyltransferase
  • Retinol O-Fatty-Acyltransferase