The enzyme, which occurs in the bacteria Azotobacter vinelandii and Sphingomonas sp. SKA58, is part of the non-phosphorylative degradation pathway for L-rhamnose. The enzyme differs in cofactor specificity from EC 1.1.1.173, L-rhamnose 1-dehydrogenase, which is specific for NAD+ and EC 1.1.1.377, L-rhamnose 1-dehydrogenase (NADP+).
The enzyme appears in viruses and cellular organisms
in putative catalytic mechanism, the C1-OH group of L-rhamnose is deprotonated by Tyr159 as a general basic catalyst, with concurrent transfer of the hydride ion to NAD(P)+, and the pKa value of its hydroxyl group is lowered by Lysl63, leading to the stabilization of the tyrosinate anion at physiological pH
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SYSTEMATIC NAME
IUBMB Comments
L-rhamnose:NAD(P)+ 1-oxidoreductase
The enzyme, which occurs in the bacteria Azotobacter vinelandii and Sphingomonas sp. SKA58, is part of the non-phosphorylative degradation pathway for L-rhamnose. The enzyme differs in cofactor specificity from EC 1.1.1.173, L-rhamnose 1-dehydrogenase, which is specific for NAD+ and EC 1.1.1.377, L-rhamnose 1-dehydrogenase (NADP+).
Substrates: the C5-OH and C6-methyl groups of L-rhamnose are recognized by specific residues of RhaDH through hydrogen bonds and hydrophobic contact, respectively, which contribute to the different substrate specificities from other aldose 1-dehydrogenases in the short-chain dehydrogenase/reductase superfamily Products: -
Substrates: the enzyme is part of an alternative pathway of L-rhamnose metabolism by which L-rhamnose is converted into pyruvate and L-lactaldehyde, through reaction steps analogous to the Entner-Doudoroff pathway Products: -
Substrates: the enzyme is part of an alternative pathway of L-rhamnose metabolism by which L-rhamnose is converted into pyruvate and L-lactaldehyde, through reaction steps analogous to the Entner-Doudoroff pathway Products: -
Substrates: the enzyme is part of an alternative pathway of L-rhamnose metabolism by which L-rhamnose is converted into pyruvate and L-lactaldehyde, through reaction steps analogous to the Entner-Doudoroff pathway Products: -
Substrates: the enzyme is part of an alternative pathway of L-rhamnose metabolism by which L-rhamnose is converted into pyruvate and L-lactaldehyde, through reaction steps analogous to the Entner-Doudoroff pathway Products: -
significant interactions with the 2'-phosphate group of NADP+, but not the 2'-hydroxyl group of NAD+, are consistent with a significant preference for NADP+ over NAD+. Structural insights into coenzyme specificity, overview
structure-function analysis, overview. The side chains of Ser146 and Tyr159, Ser148 and Gln156, Thr191, and Asn197 and one water molecular (Wat23) form hydrogen bonds with the hydroxyl groups of C1, C2, C3, and C4 of L-rhamnose, respectively. Wat23 also interacts with the side chains of Asp200, and Lys163 formed hydrogen bond network with the main chains of Ala94 and Asn117 via one water molecular (Wat41). Among these residues, Ser146-Tyr159-Lys163, corresponding to a motif of the catalytic triad, and Ala94 and Asn117 are completely conserved in SDR superfamily enzymes. Phe99 appears to be more important for enzyme catalysis than Ile196
several microorganisms can utilize L-rhamnose as a carbon and energy source through the non-phosphorylative metabolic pathway, in which L-rhamnose 1-dehydrogenase (RhaDH) catalyzes the NAD(P)+-dependent oxidization of Lrhamnose to L-rhamnono-1,4-lactone
the subunit of AvRhaDH was a single-domain protein with an alpha/beta doubly wound structure. A seven-stranded parallel beta-sheet (beta3-beta2-beta1-beta4-beta5-beta6-beta7) in the center of the molecule is sandwiched by two arrays of parallel alpha-helices (alpha1 to alpha6), which is a typical dinucleotide binding the Rossmann fold motif including the characteristic sequence Gly-X3-Gly-X-Gly; Gly12-Ala13-Ser14-Arg15-Gly16-Ile17-Gly18. Furthermore, a motif corresponding to Asn92-Asn93-Ala94-Gly95 is previously shown to be important for stabilizing this central beta-sheet in other SDR superfamily enzymes. A small domain containing the alpha7 and two 310 helixes is slightly separated from the main body of the subunit, and contained the flexible region
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CRYSTALLIZATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
purified recombinant enzyme in ligand-free, NAD+-bound, NADP+-bound, and L-rhamnose- and NAD+-bound forms, sitting drop vapor diffusion method, mixing of 500 nl of 10 mg/ml protein in 20 mM Tris/HCl, pH 8.0, and 150 mM NaCl, with 500 nl of reservoir olution containing 100 mM Tris/HCl, pH 8.5, 200 mM Li2SO4, and 25% w/v PEG 3350, with or without coenzyme, for the apoenzyme and for the NADP+-bound form,, and 100 mM Tris/HCl, pH 8.0, 200 mM NaCl, 24.5% w/v PEG 3350, and 3% v/v glycerol only for the NAD+-/L-rhamnose-bound form, equilibration against 0.07 ml of reservoir solution, at 20°C, X-ray diffraction structure determination and analysis at 1.9, 2.1, 2.4, and 1.6 A resolution, respectively, molecular replacement using the structure of 3-oxoacyl-(acyl carrier protein) reductase from Bacillus anthracis (PDB ID 2UVD) as the search model, modeling
site-directed mutagenesis, the mutant of AvRhaDH shows a Km value for NADP+ decreased by 116fold, which increases the ratio of NADP+ to NAD+ (0.188) 157fold, from that of the wild-type enzyme (18.5)