Glycerophosphodiester phosphodiesterase domain in Escherichia coli cytosolic glycerophosphodiester phosphodiesterase UgpQ and similar proteins
This subfamily corresponds to the glycerophosphodiester phosphodiesterase domain (GDPD) present in Escherichia coli cytosolic glycerophosphodiester phosphodiesterase (GP-GDE, EC 188.8.131.52), UgpQ, and similar proteins. GP-GDE plays an essential role in the metabolic pathway of E. coli. It catalyzes the degradation of glycerophosphodiesters to produce sn-glycerol-3-phosphate (G3P) and the corresponding alcohols, which are major sources of carbon and phosphate. E. coli possesses two major G3P uptake systems: Glp and Ugp, which contain genes coding for two distinct GP-GDEs. UgpQ gene from the E. coli ugp operon codes for a cytosolic phosphodiesterase GlpQ, which is the prototype of this family. Various glycerophosphodiesters, such as glycerophosphocholine (GPC), glycerophosphoethanolanmine (GPE), glycerophosphoglycerol (GPG), glycerophosphoinositol (GPI), and glycerophosphoserine (GPS), can only be hydrolyzed by UgpQ during transport at the inner side of the cytoplasmic membrane to alcohols and G3P, which is a source of phosphate. In contrast to Ca2+-dependent periplasmic phosphodiesterase GlpQ, cytosolic phosphodiesterase UgpQ requires divalent cations, such as Mg2+, Co2+, or Mn2+, for its enzyme activity.
Comment:The catalytic mechanism of glycerophosphodiester phosphodiesterases is based on the metal ion-dependent general acid-base reaction.
Comment:Based on structure evidence and site-directed mutagenesis of Thermoanaerobacter tengcongensis glycerophosphodiester phosphodiesterase, the catalytic site consists of two conserved histidine residues which serve as general acid and general base in catalyzing the hydrolysis of the 3'-5' phosphodiester bond.