Chemical structures of mammalian phospholipids and two types of acyltransferases to biosynthesize phospholipids.A, in the left panel, structures of the major classes of mammalian phospholipids are shown. "R" (highlighted in red) indicates hydrocarbon chains of fatty acids. In the right panel, several of the fatty acids most commonly esterified in mammalian phospholipids are shown. B, upper, GPATs synthesize LPA using G3P and acyl-CoA as substrates. Currently four GPATs, GPAT1 to 4, have been identified, all of the AGPAT family. B, lower, LPLATs biosynthesize phospholipids using sn-1- or sn-2-acyl LPLs and acyl-CoAs as substrates. The LPLs may be of several classes, including LPA. Currently, 14 LPLATs have been identified, all either from the AGPAT or MBOAT families.