ectonucleotide pyrophosphatase/phosphodiesterase family member 6; E-NPP 6; NPP-6; choline-specific glycerophosphodiester phosphodiesterase; glycerophosphocholine cholinephosphodiesterase (ENPP6)
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Function
- choline-specific glycerophosphodiester phosphodiesterase
- lysophospholipase C activity
- hydrolyzes lysophosphatidylcholine to form monoacylglycerol & phosphorylcholine
- hydrolyzes the classical substrate for phospholipase C, p-nitrophenyl phosphorylcholine
- does not hydrolyze lysophosphatidic acid
- preference for lysophosphatidylcholine with short (12:0 & 14:0) or polyunsaturated (18:2 & 20:4) fatty acids
- hydrolyzes glycerophosphorylcholine & sphingosylphosphoryl- choline
- does not hydrolyze the classical nucleotide phosphodiesterase substrate, p-nitrophenyl thymidine 5'-monophosphate
- does not hydrolyze diacyl phospholipids such as phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, phosphatidylglycerol or phosphatidic acid
Inhibition:
- KM=344 uM for GPC
- KM=296 uM for 12:0-LPC
- KM=440 uM for 14:0-LPC
- KM=165 uM for 16:0-LPC
- KM=434 uM for 18:2-LPC
- KM=563 uM for 20:4-LPC
- Vmax=484 nmol/min/mg enzyme with GPC as substrate
- Vmax=463 nmol/min/mg enzyme with 12:0-LPC as substrate
- Vmax=367 nmol/min/mg enzyme with 14:0-LPC as substrate
- Vmax=89 nmol/min/mg enzyme with 16:0-LPC as substrate
- Vmax=285 nmol/min/mg enzyme with 18:2-LPC as substrate
- Vmax=470 nmol/min/mg enzyme with 20:4-LPC as substrate
- pH dependence: optimum pH is 8.5-7.5
Structure
- belongs to the nucleotide pyrophosphatase/phosphodiesterase family
Compartment
- cell membrane,
- a minor secreted form
Expression
predominantly expressed in kidney & brain