Adipose triglyceride lipase, also known as patatin-like phospholipase domain-containing protein 2 and ATGL, is an enzyme that in humans is encoded by the PNPLA2 gene. ATGL catalyses the first reaction of lipolysis, where triacylglycerols are hydrolysed to diacylglycerols. ATGL has very high substrate specificity for triacylglycerols. It contains a catalytic dyad using serine-aspartic acid. ATGL catalyses the first reaction of lipolysis. It hydrolysis triacylglycerols to diacylglycerols by attacking the fatty acid attached to carbon-3 of glycerol. ATGL acts as a control mechanism of lipolysis, as variations in diacylglycerol concentration impact enzymes in later stages of lipolysis.