Phosphorylcholine esterase

Figure 35. Active site structures of (A) Fe VZH red kidney bean purple acid phosphatase in complex with phosphate (PDB code 4KBP), (B) phosphorylcholine esterase domain of the virulence factor choline-binding protein E from Streptococcus pneumoniae (PDB code IWRA), and (C) rubredoxinioxygen oxidoreductase (ROO) from Desulfovibrio gigas (PDB code 1E5D).

Simple esters are split by extracts of all tissues. The number of different esterases is not known. The digestive esterases produced by the pancreas are called lipases because they hydrolyze the triglycerides that are the most prominent lipids. They also hydrolyze simple esters. A special group of enzymes hydrolyze phospholipids. So-called lecithinase A removes one acyl group from lecithin to form lysolecithin, which causes hemolysis of erythrocytes. This enzyme has been crystallized from snake venom. Other animal toxins and bacteria also form lysolecithin by hydrolysis of lecithin. The removal of the second acyl group is catalyzed by phospholipase B, which has been studied in plant and animal extracts and also occurs in bacteria. Other enzymes, phospholipase C and D, specifically remove phosphorylcholine and choline, respectively, from lecithin. 

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