[trahy-glis-uh-rahyd, -er-id]

Any of an important class of naturally occurring lipids, esters in which three molecules of fatty acids are linked to glycerol. The three fatty acids may be all the same kind or different kinds. The types of triglycerides in animals vary with the species and the fats in their food. In mammals they are stored in adipose tissue until needed and then broken down to the glycerol and fatty acids. Many vegetable triglycerides (oils) are liquid at room temperature, unlike those of animals, and tend to contain a greater variety of fatty acids. In alkali, triglycerides break down to form glycerol and three molecules of soap (saponification).

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In enzymology, a triacylglycerol---sterol O-acyltransferase is an enzyme that catalyzes the chemical reaction

triacylglycerol + a 3beta-hydroxysterol rightleftharpoons diacylglycerol + a 3beta-hydroxysterol ester

Thus, the two substrates of this enzyme are triacylglycerol and 3beta-hydroxysterol, whereas its two products are diacylglycerol and 3beta-hydroxysterol ester.

This enzyme belongs to the family of transferases, specifically those acyltransferases transferring groups other than aminoacyl groups. The systematic name of this enzyme class is triacylglycerol:3beta-hydroxysterol O-acyltransferase. This enzyme is also called triacylglycerol:sterol acyltransferase.


  • Zimowski J and Wojciechowski ZA "Acyl donors for sterol esterification by cell-free preparations from Sinapis alba roots". Phytochemistry 20 1799–1803.

External links

The CAS registry number for this enzyme class is .

Gene Ontology (GO) codes

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