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  • Title: Polyol-specific long-chain dehydrogenases/reductases of mannitol metabolism in Aspergillus fumigatus: biochemical characterization and pH studies of mannitol 2-dehydrogenase and mannitol-1-phosphate 5-dehydrogenase.
    Author: Krahulec S, Armao GC, Bubner P, Klimacek M, Nidetzky B.
    Journal: Chem Biol Interact; 2009 Mar 16; 178(1-3):274-82. PubMed ID: 18983992.
    Abstract:
    Functional genomics data suggests that the metabolism of mannitol in the human pathogen Aspergillus fumigatus involves the action of two polyol-specific long-chain dehydrogenases/reductases, mannitol-1-phosphate 5-dehydrogenase (M1PDH) and mannitol 2-dehydrogenase (M2DH). The gene encoding the putative M2DH was expressed in Escherichia coli, and the purified recombinant protein was characterized biochemically. The predicted enzymatic function of a NAD(+)-dependent M2DH was confirmed. The enzyme is a monomer of 58kDa in solution and does not require metals for activity. pH profiles for M2DH and the previously isolated M1PDH were recorded in the pH range 6.0-10.0 for the oxidative and reductive direction of the reactions under conditions where substrate was limiting (k(cat)/K) or saturating (k(cat)). The pH-dependence of logk(cat) was usually different from that of log(k(cat)/K), suggesting that more than one step of the enzymatic mechanism was affected by changes in pH. The greater complexity of the pH profiles of log(k(cat)/K) for the fungal enzymes as compared to the analogous pH profiles for M2DH from Pseudomonas fluorescens may reflect sequence changes in vicinity of the conserved catalytic lysine.
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