Diacylglycerol (DAG) found within cells is derived from two broad sources. First, in thede novobiosynthetic pathway, glycerol 3-phosphate is converted by two acylation steps to phosphatidic acid (PA), which is converted to DAG by phosphatidate phosphohydrolase (PPH). This is part of the pathway for synthesis of triacylglycerol and phospholipids from the carbon backbone of glycerol. Second, DAG is formed from phospholipids by the actions of phospholipases. It is this second process that is directly regulated by cell-surface receptors, and to which this chapter is addressed.
