CD203c; ectonucleotide pyrophosphatase/phosphodiesterase family member 3; E-NPP 3; phosphodiesterase I beta; PD-Ibeta; phosphodiesterase I/nucleotide pyrophosphatase 3; includes: alkaline phosphodiesterase I; nucleotide pyrophosphatase (ENPP3, PDNP3, NPPase)
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Function
- cleaves a variety of phosphodiester & phosphosulfate bonds including deoxynucleotides, nucleotide sugars, & NAD
- hydrolytically removes 5'-nucleotides successively from the 3'-hydroxy termini of 3'-hydroxy-terminated oligonucleotides
- at low concentrations of ATP, a phosphorylated active site intermediate is formed which inhibits further ATP hydrolysis
- the active SMB domain may be permitted disulfide bond heterogeneity
- 2 alternate disulfide patterns based on 3D structures are described with 1 disulfide bond conserved in both
- binds 2 divalent metal cations per subunit (probable)
Structure
- N-glycosylation is necessary for correct trafficking to the apical surface, but is not the apical targeting signal
- belongs to the nucleotide
- pyrophosphatase/phosphodiesterase family
- contains 2 SMB (somatomedin-B) domains
Compartment
- membrane; single-pass type 2 membrane protein (putative)
- secreted
- located at the apical surface in intestinal & kidney epithelial cells
- located at the cell surface of basophils, & at the apical plasma membrane of bile duct cells
- secreted into plasma, & into lumen lined by epithelial cells
Expression
- expressed in bile ducts, prostate, uterus & colon
- expressed on basophils, mast cells & their progenitors
- up-regulated by stimulation by allergen or by cross-linking with IgE
- IgE-mediated activation is enhanced by tetradecanoyl phorbol acetate, a stimulator of the PKC pathway, & inhibited by the P13 kinase inhibitors, LY294002 & wortmannin
Pathology
- up-regulated in invasive bile duct cancers