Abstract
Oenococcus oeni, a lactic acid bacterium, possesses a lysine racemase, which has a specific activity towards basic amino acids. A comparison of amino acid residues around the active site suggested that Ile222 and Tyr354 of the Geobacillus stearothermophilus alanine racemase, which shares 60% sequence similarity with lysine racemase, were replaced by Thr224 and Trp355 in the O. oeni lysine racemase. T224I/W355Y double mutations significantly decreased the activity of lysine racemase, whereas I222T/Y354W double mutations endowed alanine racemase with lysine racemization activity. These results suggest that the two residues play an important role in lysine racemization.
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