Crude mannose isomerase preparation from Xanthomonas rubrilineans S-48 which converts D-mannose to D-fructose was further purified by ammonium sulfate fractionation and DEAE-cellulose column chromatography. The specific activity of the purified enzyme solution was about 35-fold of original crude preparation. By using this purified enzyme solution, several enzymatic properties were investigated.
(1) The Michaelis constant was 1.2×10^-2M. (2) The enzyme was sensitive against temperature, but Ca⁺⁺ protected the enzyme to some extent from the effect of temperature. (3) The enzyme was stable in the pH range from 6 to 9. (4) The enzyme was not inhibited by glucose, xylose, mannitol, sorbitol, mannonic acid, mannuronic acid and so on, but strongly inhibited by D-arabinose and L-fucose, and Ki values of these inhibitors were 1.1×10^-2M and 7.1×10^-4M respectively.

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