Mannitol metabolism in the mycorrhizal fungus,Piloderma croceum
Experimental Mycology(1986)
摘要
NADP-specific mannitol dehydrogenase, mannitol-1-phosphatase, and hexokinase were detected in, and partly purified from mycelia of, the mycorrhizal fungus,Piloderma croceum. Mannitol-1-phosphate dehydrogenase activity was low or absent under the growth conditions used. Substrate specificity for mannitol-1-phosphatase was limited to mannitol 1-phosphate, with an activity of ca. 20% or less with the other sugar phosphates tested. TheKm (fructose) for mannitol dehydrogenase and hexokinase favored the forward reaction of mannitol ⇄ fructose ⇄ fructose 6-phosphate with net transformation of mannitol to fructose 6-phosphate. Zinc ion was a competitive inhibitor for mannitol dehydrogenase with respect to mannitol, with aKi of 5.5 μM. The properties of mannitol-1-phosphatase, mannitol dehydrogenase, and hexokinase suggest that mannitol dehydrogenase is used for mannitol utilization and the evidence taken together suggests that mannitol is synthesized by the action of mannitol-1-phosphatase and an inducible mannitol-1-phosphate dehydrogenase. However, direct evidence for an inducible mannitol-1-phosphate dehydrogenase is still missing and our failure to detect mannitol in our cultures indicates that the proper condition for such an induction was not present.
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关键词
mannitol metabolism,mycorrhizal fungus,Piloderma croceum,mannitol-1-phosphate dehydrogenase,mannitol dehydrogenase,mannitol-1-phosphatase
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