SUMMARY: Activities of the polyol dehydrogenases of f. sp. were surveyed by measuring polyol-dependent rates of reduction of NAD and NADP in cell-free extracts of axenically-grown mycelia. Seven of the eight polyols tested caused NADP reduction, with highest activity for -glucitol, followed by -arabitol, xylitol, erythritol, galactitol and ribitol, and low activity with -arabitol; only -mannitol failed to support activity. Inactivation rates were consistent with at least three separate enzymes, specific for -glucitol, xylitol and -arabitol respectively, with apparent values of 170--198 mM for xylitol and -glucitol ( for NADP 36--55 μM), and 34 mM for -arabitol ( for NADP 1·2 μM). The NADP-dependent activities were almost completely inhibited by 2 mM-dithiothreitol, in contrast to the NAD-dependent activities, which were stimulated. NAD-dependent activity was highest with -mannitol, followed by successively lower activities with -arabitol, xylitol and -glucitol, with no activity with any of the other polyols; each of the four active polyols appeared to be oxidized by a different enzyme. All four NAD-dependent activities were rapidly lost after Sephadex treatment of crude extracts.


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