a CDP-1,2-diacyl-sn-glycerol + H2O = a 1,2-diacyl-sn-glycero-3-phosphate + CMP + 2 H(+) Phospholipid metabolism; CDP-diacylglycerol degradation; phosphatidate from CDP-diacylglycerol: step 1/1. Belongs to the Cdh family.