Histidine 167 Is the Phosphate Acceptor in Glucose-6-phosphatase-β Forming a Phosphohistidine Enzyme Intermediate during Catalysis
Copyright policy )Histidine 167 Is the Phosphate Acceptor in Glucose-6-phosphatase-β Forming a Phosphohistidine Enzyme Intermediate during Catalysis
The glucose-6-phosphatase (Glc-6-Pase) family comprises two active endoplasmic reticulum (ER)-associated isozymes: the liver/kidney/intestine Glc-6-Pase-alpha and the ubiquitous Glc-6-Pase-beta. Both share similar kinetic properties. Sequence alignments predict the two proteins are structurally similar. During glucose 6-phosphate (Glc-6-P) hydrolysis, Glc-6-Pase-alpha, a nine-transmembrane domain protein, forms a covalently bound phosphoryl enzyme intermediate through His(176), which lies on the lumenal side of the ER membrane. We showed that Glc-6-Pase-beta is also a nine-transmembrane domain protein that forms a covalently bound phosphoryl enzyme intermediate during Glc-6-P hydrolysis. However, the intermediate was not detectable in Glc-6-Pase-beta active site mutants R79A, H114A, and H167A. Using [(32)P]Glc-6-P coupled with cyanogen bromide mapping, we demonstrated that the phosphate acceptor in Glc-6-Pase-beta is His(167) and that it lies inside the ER lumen with the active site residues, Arg(79) and His(114). Therefore Glc-6-Pase-alpha and Glc-6-Pase-beta share a similar active site structure, topology, and mechanism of action.
- National Institutes of Health United States
- National Institute of Health Pakistan
Binding Sites, Hydrolysis, Blotting, Western, Cell Membrane, Molecular Sequence Data, Endoplasmic Reticulum, Catalysis, Adenoviridae, Epitopes, Kinetics, Glucose, Microsomes, COS Cells, Glucose-6-Phosphatase, Animals, Humans, Histidine, Amino Acid Sequence, Cyanogen Bromide, Isoelectric Focusing
Binding Sites, Hydrolysis, Blotting, Western, Cell Membrane, Molecular Sequence Data, Endoplasmic Reticulum, Catalysis, Adenoviridae, Epitopes, Kinetics, Glucose, Microsomes, COS Cells, Glucose-6-Phosphatase, Animals, Humans, Histidine, Amino Acid Sequence, Cyanogen Bromide, Isoelectric Focusing
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