| Structural highlights
Function
[Q6T1X6_ANETH] Reductase that catalyzes the conversion of GDP-6-deoxy-D-mannose to GDP-4-dehydro-6-deoxy-D-mannose (GDP-D-rhamnose).[1] [2]
Evolutionary Conservation
Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.
Publication Abstract from PubMed
The rare 6-deoxysugar D-rhamnose is a component of bacterial cell surface glycans, including the D-rhamnose homopolymer produced by Pseudomonas aeruginosa, called A-band O polysaccharide. GDP-D-rhamnose synthesis from GDP-D-mannose is catalyzed by two enzymes. The first is a GDP-D-mannose-4,6-dehydratase (GMD). The second enzyme, RMD, reduces the GMD product (GDP-6-deoxy-D-lyxo-hexos-4-ulose) to GDP-d-rhamnose. Genes encoding GMD and RMD are present in P. aeruginosa, and genetic evidence indicates they act in A-band O-polysaccharide biosynthesis. Details of their enzyme functions have not, however, been previously elucidated. We aimed to characterize these enzymes biochemically, and to determine the structure of RMD to better understand what determines substrate specificity and catalytic activity in these enzymes. We used capillary electrophoresis and NMR analysis of reaction products to precisely define P. aeruginosa GMD and RMD functions. P. aeruginosa GMD is bifunctional, and can catalyze both GDP-d-mannose 4,6-dehydration and the subsequent reduction reaction to produce GDP-D-rhamnose. RMD catalyzes the stereospecific reduction of GDP-6-deoxy-D-lyxo-hexos-4-ulose, as predicted. Reconstitution of GDP-D-rhamnose biosynthesis in vitro revealed that the P. aeruginosa pathway may be regulated by feedback inhibition in the cell. We determined the structure of RMD from Aneurinibacillus thermoaerophilus at 1.8 A resolution. The structure of A. thermoaerophilus RMD is remarkably similar to that of P. aeruginosa GMD, which explains why P. aeruginosa GMD is also able to catalyze the RMD reaction. Comparison of the active sites and amino acid sequences suggests that a conserved amino acid side chain (Arg185 in P. aeruginosa GMD) may be crucial for orienting substrate and cofactor in GMD enzymes.
The structural basis for catalytic function of GMD and RMD, two closely related enzymes from the GDP-D-rhamnose biosynthesis pathway.,King JD, Poon KK, Webb NA, Anderson EM, McNally DJ, Brisson JR, Messner P, Garavito RM, Lam JS FEBS J. 2009 May;276(10):2686-700. PMID:19459932[3]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Kneidinger B, Graninger M, Adam G, Puchberger M, Kosma P, Zayni S, Messner P. Identification of two GDP-6-deoxy-D-lyxo-4-hexulose reductases synthesizing GDP-D-rhamnose in Aneurinibacillus thermoaerophilus L420-91T. J Biol Chem. 2001 Feb 23;276(8):5577-83. Epub 2000 Nov 28. PMID:11096116 doi:http://dx.doi.org/10.1074/jbc.M010027200
- ↑ King JD, Poon KK, Webb NA, Anderson EM, McNally DJ, Brisson JR, Messner P, Garavito RM, Lam JS. The structural basis for catalytic function of GMD and RMD, two closely related enzymes from the GDP-D-rhamnose biosynthesis pathway. FEBS J. 2009 May;276(10):2686-700. PMID:19459932 doi:10.1111/j.1742-4658.2009.06993.x
- ↑ King JD, Poon KK, Webb NA, Anderson EM, McNally DJ, Brisson JR, Messner P, Garavito RM, Lam JS. The structural basis for catalytic function of GMD and RMD, two closely related enzymes from the GDP-D-rhamnose biosynthesis pathway. FEBS J. 2009 May;276(10):2686-700. PMID:19459932 doi:10.1111/j.1742-4658.2009.06993.x
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