2bes
From Proteopedia
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STRUCTURE OF MYCOBACTERIUM TUBERCULOSIS RIBOSE-5-PHOSPHATE ISOMERASE, RPIB, RV2465C, IN COMPLEX WITH 4-PHOSPHO-D-ERYTHRONOHYDROXAMIC ACID.
Overview
Ribose-5-phosphate isomerase (Rpi), an important enzyme in the pentose, phosphate pathway, catalyzes the interconversion of ribulose 5-phosphate, and ribose 5-phosphate. Two unrelated isomerases have been identified, RpiA and RpiB, with different structures and active site residues. The, reaction catalyzed by both enzymes is thought to proceed via a high energy, enediolate intermediate, by analogy to other carbohydrate isomerases. Here, we present studies of RpiB from Mycobacterium tuberculosis together with, small molecules designed to resemble the enediolate intermediate. The, relative affinities of these inhibitors for RpiB have a different pattern, than that observed previously for the RpiA from spinach. X-ray structures, of RpiB in complex with the inhibitors 4-phospho-d-erythronohydroxamic, acid (K(m) 57 microm) and 4-phospho-d-erythronate (K(i) 1.7 mm) refined to, resolutions of 2.1 and 2.2 A, respectively, allowed us to assign roles for, most active site residues. These results, combined with docking of the, substrates in the position of the most effective inhibitor, now allow us, to outline the reaction mechanism for RpiBs. Both enzymes have residues, that can catalyze opening of the furanose ring of the ribose 5-phosphate, and so can improve the efficiency of the reaction. Both enzymes also have, an acidic residue that acts as a base in the isomerization step. A lysine, residue in RpiAs provides for more efficient stabilization of the, intermediate than the corresponding uncharged groups of RpiBs; this same, feature lies behind the more efficient binding of RpiA to, 4-phospho-d-erythronate.
About this Structure
2BES is a Single protein structure of sequence from Mycobacterium tuberculosis with RES as ligand. Active as Ribose-5-phosphate isomerase, with EC number 5.3.1.6 Known structural/functional Site: . Full crystallographic information is available from OCA.
Reference
Competitive inhibitors of Mycobacterium tuberculosis ribose-5-phosphate isomerase B reveal new information about the reaction mechanism., Roos AK, Burgos E, Ericsson DJ, Salmon L, Mowbray SL, J Biol Chem. 2005 Feb 25;280(8):6416-22. Epub 2004 Dec 7. PMID:15590681
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