Catalytic domain of uncharacterized hypothetical proteins similar to eukaryotic phosphatidylinositol-specific phospholipase C, X domain containing proteins
This subfamily corresponds to the catalytic domain present in a group of uncharacterized hypothetical proteins found in bacteria and fungi, which are similar to eukaryotic phosphatidylinositol-specific phospholipase C, X domain containing proteins (PI-PLCXD). The typical eukaryotic phosphoinositide-specific phospholipase C (PI-PLC, EC 184.108.40.206) has a multidomain organization that consists of a PLC catalytic core domain, and various regulatory domains. The catalytic core domain is assembled from two highly conserved X- and Y-regions split by a divergent linker sequence. In contrast, eukaryotic PI-PLCXDs contain a single TIM-barrel type catalytic domain, X domain, and are more closely related to bacterial PI-PLCs, which participate in Ca2+-independent PI metabolism, hydrolyzing the membrane lipid phosphatidylinositol (PI) to produce phosphorylated myo-inositol and diacylglycerol (DAG). Although the biological function of eukaryotic PI-PLCXDs still remains unclear, it may distinct from that of typical eukaryotic PI-PLCs.
Comment:Both prokaryotic and eukaryotic PI-PLCs utilize a similar catalytic mechanism, a general base and acid catalysis involving two well conserved histidines. It consists of two steps, a phosphotransfer and a phosphodiesterase reaction.
Comment:Based on structure evidence of the catalytic site in Bacillus cereus phosphatidylinositol-specific phospholipase C.