PMID:12805358
| Citation |
Meredith, TC and Woodard, RW (2003) Escherichia coli YrbH is a D-arabinose 5-phosphate isomerase. J. Biol. Chem. 278:32771-7 |
|---|---|
| Abstract |
A gene encoding for arabinose 5-phosphate isomerase (API), which catalyzes the interconversion of d-ribulose 5-phosphate (Ru5P) and d-arabinose 5-phosphate (A5P), has been identified from the genome of Escherichia coli K-12. API is the first enzyme in the biosynthesis of 3-deoxy-d-manno-octulosonate (KDO), a sugar moiety located in the lipopolysaccharide layer of most Gram-negative bacteria. The API gene yrbH is located next to the recently identified specific KDO 8-P phosphatase gene, yrbI. The 328-amino acid open reading frame yrbH was cloned, overexpressed, and characterized. The purified recombinant enzyme is a tetramer and is sensitive to inhibition by zinc cations. API has optimal activity at pH 8.4 and catalytic residues with estimated pKa values of 6.55 +/- 0.04 and 10.34 +/- 0.07. The enzyme is specific for A5P and Ru5P, with apparent Km values of 0.61 +/- 0.06 mm for A5P and 0.35 +/- 0.08 mm for Ru5P. The apparent kcat in the A5P to Ru5P direction is 157 +/- 4 s-1, and in the Ru5P to A5P direction it is 255 +/- 16 s-1. The value of Keq (Ru5P/A5P) is 0.50 +/- 0.06. Homology searches of the E. coli genome suggest yrbH may be one of multiple genes that encode proteins with API activity. |
| Links |
PubMed Online version:10.1074/jbc.M303661200 |
| Keywords |
Aldose-Ketose Isomerases/chemistry; Aldose-Ketose Isomerases/metabolism; Amino Acid Sequence; Catalysis; Cations; Cloning, Molecular; Electrophoresis, Polyacrylamide Gel; Escherichia coli/enzymology; Escherichia coli/metabolism; Escherichia coli Proteins/chemistry; Escherichia coli Proteins/metabolism; Hydrogen-Ion Concentration; Kinetics; Lipopolysaccharides/metabolism; Magnetic Resonance Spectroscopy; Metals/chemistry; Models, Chemical; Molecular Sequence Data; Molecular Weight; Open Reading Frames; Recombinant Proteins/chemistry; Recombinant Proteins/metabolism; Sequence Homology, Amino Acid; Substrate Specificity; Zinc/chemistry |
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