The protein encoded by this gene is an enzyme that catalyzes the synthesis of diacylglycerol from 2-monoacylglycerol and fatty acyl-CoA. The encoded protein is important in the uptake of dietary fat by the small intestine. This protein forms a complex with diacylglycerol O-acyltransferase 2 in the endoplasmic reticulum, and this complex catalyzes the synthesis of triacylglycerol. [provided by RefSeq, Dec 2015].