Acyl coenzyme A dependent retinol esterification by acyl coenzyme A: diacylglycerol acyltransferase 1.
We provide biochemical evidence that enzymes involved in the synthesis of triacylglycerol, namely acyl coenzyme A:diacylglycerol acyltransferase (DGAT) and acyl coenzyme A:monoacylglycerol acyltransferase (MGAT), are capable of carrying out the acyl coenzyme A:retinol acyltransferase (ARAT) reaction. Among them, DGAT1 appears to have the highest specific activity. The apparent K(m) values of recombinant DGAT1/ARAT for retinol and palmitoyl coenzyme A were determined to be 25.9+/-2.1 microM and 13.9+/-0.3 microM, respectively, both of which are similar to the values previously determined for ARAT in native tissues. A novel selective DGAT1 inhibitor, XP620, inhibits recombinant DGAT1/ARAT at the retinol recognition site. In the differentiated Caco-2 cell membranes, XP620 inhibits approximately 85% of the Caco-2/ARAT activity indicating that DGAT1/ARAT may be the major source of ARAT activity in these cells. Of the two most abundant fatty acyl retinyl esters present in the intact differentiated Caco-2 cells, XP620 selectively inhibits retinyl-oleate formation without influencing the retinyl-palmitate formation. Using this inhibitor, we estimate that approximately 64% of total retinyl ester formation occurs via DGAT1/ARAT. These studies suggest that DGAT1/ARAT is the major enzyme involved in retinyl ester synthesis in Caco-2 cells.
Orland
Michael D
MD
Department of Obesity and Metabolic Research, Pharmaceutical Research Institute, Bristol-Myers Squibb Company, Princeton, NJ 08543-5400, USA.
Anwar
Kamran
K
Cromley
Debra
D
Chu
Ching-Hsuen
CH
Chen
Luping
L
Billheimer
Jeffrey T
JT
Hussain
M Mahmood
MM
Cheng
Dong
D
D000217:Acyltransferases / Q000378:metabolism; D000818:Animals; D018938:Caco-2 Cells; D051048:Diacylglycerol O-Acyltransferase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006573:Heterocyclic Compounds, 1-Ring / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D051142:Retinol O-Fatty-Acyltransferase / Q000378:metabolism*; D014801:Vitamin A / Q000378:metabolism*
D006573:Heterocyclic Compounds, 1-Ring; C506265:XP 620; D014801:Vitamin A; D000217:Acyltransferases; C494881:DGAT1 protein, human; D051048:Diacylglycerol O-Acyltransferase; C021802:2-acylglycerol O-acyltransferase; D051142:Retinol O-Fatty-Acyltransferase