Effect of sugar and monoglyceride on fatty acid esterification.

The effect of hexose and monoolein on fatty acid esterification was studied in everted rings of rat jejunum. By use of [3H]oleic acid and [U-14C]glucose, esterification via both phosphatidic acid and monoglyceride pathways was quantified. Our results showed that 1) metabolizable sugars stimulate fatty acids esterification regardless of their mode of transport; 2) in the presence of glucose alone, in vitro fatty acid esterification is mediated entirely by the phosphatidic acid pathway; 3) glucose stimulates both esterification pathways in the presence of monoolein; 4) monoolein stimulates only the monoglyceride pathway and has no effect on the phosphatidic acid pathway; and 5) the rate-limiting factor in the presence of monoolein alone is the formation of acyl-CoA, whereas in the presence of glucose alone, the rate-limiting factor is the formation of alpha-glycerophosphate.