Phosphatidylcholine (PC) turnover in the yeast ER. Turnover reactions degrading PC are indicated by red arrows, acyl chain exchange reactions (PC-DRP) by green arrows, and the enzymes involved in blue, with those localized to the ER in bold. The putative conversion of PC to lyso-PC by a phospholipase A (PLA) or transacylase (AT) referred to by the dashed green arrow has not been demonstrated in vivo. The methylation of phosphatidylethanolamine (PE) and the CDP-choline pathway both synthesizing PC de novo are indicated in grey. DAG, diacylglycerol; FA, fatty acid; G3P, glycerol-3-phosphate; GPC, glycerophosphocholine.