ABSTRACT
Two complexes of the enzyme phosphomannomutase/phosphoglucomutase (PMM/PGM) from Pseudomonas aeruginosa with a slow substrate and with an inhibitor have been characterized by X-ray crystallography. Both ligands induce an interdomain rearrangement in the enzyme that creates a highly buried active site. Comparisons with enzyme-substrate complexes show that the inhibitor xylose 1-phosphate utilizes many of the previously observed enzyme-ligand interactions. In contrast, analysis of the ribose 1-phosphate complex reveals a combination of new and conserved enzyme-ligand interactions for binding. The ability of PMM/PGM to accommodate these two pentose phosphosugars in its active site may be relevant for future efforts towards inhibitor design.
Subject(s)
Phosphoglucomutase/chemistry , Phosphotransferases (Phosphomutases)/chemistry , Pseudomonas aeruginosa/enzymology , Bacterial Proteins/antagonists & inhibitors , Bacterial Proteins/chemistry , Bacterial Proteins/metabolism , Binding Sites , Crystallography, X-Ray , Enzyme Inhibitors/chemistry , Enzyme Inhibitors/pharmacology , Ligands , Models, Molecular , Pentosephosphates/chemistry , Pentosephosphates/pharmacology , Phosphoglucomutase/antagonists & inhibitors , Phosphoglucomutase/metabolism , Phosphotransferases (Phosphomutases)/antagonists & inhibitors , Phosphotransferases (Phosphomutases)/metabolism , Protein Conformation , Ribosemonophosphates/chemistry , Ribosemonophosphates/pharmacologyABSTRACT
The alpha-D-phosphohexomutase superfamily is composed of four related enzymes that catalyze a reversible, intramolecular phosphoryl transfer on their sugar substrates. The enzymes in this superfamily play important and diverse roles in carbohydrate metabolism in organisms from bacteria to humans. Recent structural and mechanistic studies of one member of this superfamily, phosphomannomutase/phosphoglucomutase (PMM/PGM) from Pseudomonas aeruginosa, have provided new insights into enzyme mechanism and substrate recognition. Here we use sequence-sequence and sequence-structure comparisons via evolutionary trace analysis to examine 71 members of the alpha-D-phosphohexomutase superfamily. These analyses show that key residues in the active site, including many of those involved in substrate contacts in the P. aeruginosa PMM/PGM complexes, are conserved throughout the enzyme family. Several important regions show class-specific differences in sequence that appear to be correlated with differences in substrate specificity exhibited by subgroups of the family. In addition, we describe the translocation of a 20-residue segment containing the catalytic phosphoserine of phosphoacetylglucosamine mutase, which uniquely identifies members of this subgroup.
