Glycerophosphodiester phosphodiesterase domain of Escherichia coli (GlpQ) and similar proteins
This subfamily corresponds to the glycerophosphodiester phosphodiesterase domain (GDPD) present in Escherichia coli periplasmic glycerophosphodiester phosphodiesterase (GP-GDE, EC 184.108.40.206), GlpQ, 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 different GP-GDEs. GlpQ gene from the E. coli glp operon codes for a periplasmic phosphodiesterase GlpQ, which is the prototype of this family. GlpQ is a dimeric enzyme that hydrolyzes periplasmic glycerophosphodiesters, such as glycerophosphocholine (GPC), glycerophosphoethanolanmine (GPE), glycerophosphoglycerol (GPG), glycerophosphoinositol (GPI), and glycerophosphoserine (GPS), to the corresponding alcohols and G3P, which is subsequently transported into the cell through the GlpT transport system. Ca2+ is required for the enzymatic activity of GlpQ. This family also includes a surface-exposed lipoprotein, protein D (HPD), from Haemophilus influenza Type b and nontypeable strains, which shows very high sequence similarity with E. coli GlpQ. HPD has been characterized as a human immunoglobulin D-binding protein with glycerophosphodiester phosphodiesterase activity. It can hydrolyze phosphatidylcholine from host membranes to produce free choline on the lipopolysaccharides on the surface of pathogenic bacteria.
Comment:The catalytic mechanism of glycerophosphodiester phosphodiesterases is based on the metal ion-dependent general acid-base reaction.
Structure:1YDY; The catalytic site of Escherichia coli periplasmic glycerophosphodiester phosphodiesterase consists of two conserved histidine residues, which serve as general acid and general base in catalyzing the hydrolysis of the 3'-5' phosphodiester bond. - View structure with Cn3D