1997 Volume 61 Issue 10 Pages 1778-1782
We purified a novel type of D-mannitol dehydrogenase, which contains a c-type cytochrome and an unknown chromophore in the soluble fraction of an acetic acid bacterium, Acetobacter xylinum KU-1, to homogeneity. The enzyme showed the maximum activity at pH 5 and 40°C. It was stable up to 60°C at pH 6, and was inhibited by Hg2+ and p-quinone (Ki=0.18 mM). The molecular weight of the enzyme was about 140, 000, and those of the subunits were 69, 000, 51, 000, and 20, 000; the enzyme is hetero-trimeric and contained 8 g-atoms of Fe per mole. The α-helix content was estimated to be about 52.9%. The enzyme catalyzed phenazine methosulfate dependent oxidation of D-mannitol with an apparent Km of 98μM (for D-mannitol) and Vmax of 213 μmol/min/mg. The reduced form of the enzyme showed the absorption maxima at 386, 416, 480, 518, 550, and 586 nm, which are attributable to a c-type cytochrome in the enzyme.
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