In enzymology, a galactosylacylglycerol O-acyltransferase (EC 2.3.1.141) is an enzyme that catalyzes the chemical reaction

acyl-[acyl-carrier-protein] + sn-3-D-galactosyl-sn-2-acylglycerol ${\displaystyle \rightleftharpoons }$ [acyl-carrier-protein] + D-galactosyldiacylglycerol

Thus, the two substrates of this enzyme are [[acyl-[acyl-carrier-protein]]] and sn-3-D-galactosyl-sn-2-acylglycerol, whereas its two products are acyl-carrier-protein and D-galactosyldiacylglycerol.

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 acyl-[acyl-carrier-protein]:D-galactosylacylglycerol O-acyltransferase. Other names in common use include acyl-acyl-carrier protein: lysomonogalactosyldiacylglycerol, acyltransferase, and acyl-ACP:lyso-MGDG acyltransferase. This enzyme participates in glycerolipid metabolism.

• Chen HH, Wickrema A, Jaworski JG (1988). "Acyl-acyl-carrier protein: lysomonogalactosyldiacylglycerol acyltransferase from the cyanobacterium Anabaena variabilis". Biochim. Biophys. Acta. 963 (3): 493–500. doi:10.1016/0005-2760(88)90317-7. PMID 3143419.