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1mbb
From Proteopedia
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OXIDOREDUCTASE
Overview
UDP-N-acetylenolpyruvylglucosamine reductase (MurB), a peptidoglycan, biosynthetic enzyme from Escherichia coli, reduces both (E)- and, (Z)-isomers of enolbutyryl-UDP-GlcNAc, C4 analogs of the physiological C3, enolpyruvyl substrate, to UDP-methyl-N-acetylmuramic acid in the presence, of NADPH. The X-ray crystal structure of the, (E)-enolbutyryl-UDP-GlcNAc-MurB complex is similar to that of the, enolpyruvyl-UDP-GlcNAc-MurB complex. In both structures the groups thought, to be involved in hydride transfer to C3 and protonation at C2 of the enol, ether substrate are arranged anti relative to the enol double bond. The, stereochemical outcome of reduction of (E)-enolbutyryl-UDP-GlcNAc by NADPD, in D2O is thus predicted to yield a (2R,3R)-dideuterio product. This was, validated by conversion of the 2,3-dideuterio-UDP-methyl-N-acetylmuramic, acid product to 2,3-dideuterio-2-hydroxybutyrate, which was shown to be, (2R) by enzymatic analysis and (3R) by NMR comparison to authentic, (2R,3R)- and (2R,3S)-2,3-dideuterio-2-hydroxybutyrate. Remarkably, the, (E)-enolbutyryl-UDP-GlcNAc was found to partition between reduction to, UDP-methyl-N-acetylmuramic and isomerization to the (Z)-substrate isomer, in the MurB active site, indicative of a C2 carbanion/enol species that is, sufficiently long-lived to rotate around the C2-C3 single bond during, catalysis.
About this Structure
1MBB is a Single protein structure of sequence from Escherichia coli with EEB and FAD as ligands. Active as UDP-N-acetylmuramate dehydrogenase, with EC number 1.1.1.158 Full crystallographic information is available from OCA.
Reference
(E)-enolbutyryl-UDP-N-acetylglucosamine as a mechanistic probe of UDP-N-acetylenolpyruvylglucosamine reductase (MurB)., Lees WJ, Benson TE, Hogle JM, Walsh CT, Biochemistry. 1996 Feb 6;35(5):1342-51. PMID:8634262
Page seeded by OCA on Tue Nov 20 21:17:47 2007
