Journal
JOURNAL OF BIOTECHNOLOGY
Volume 133, Issue 3, Pages 334-342Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jbiotec.2007.10.013
Keywords
pyranose dehydrogenase; sugar oxidoreductase; galactose conversion; enzyme technology
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Funding
- Austrian Science Fund FWF [P 16836] Funding Source: Medline
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Pyranose dehydrogenase (PDH) of the mushroom Agaricus meleagris was purified from mycelial culture media to substantial homogeneity using ion-exchange and hydrophobic interaction chromatography. The native enzyme is a monomeric polypeptide with a molecular mass of 66,547 Da as determined by matrix-assisted laser desorption/ionisation mass spectrometry containing similar to 7% carbohydrate and covalently bound flavin adenine dinucleotide. The enzyme exhibited a broad sugar substrate tolerance, oxidizing different aldopyranoses to the corresponding C-2 or C-2,3 (di)dehydro sugars. Preferred electron donors with the highest k(cat)/K-m values were major sugar constituents of cellulose and hemicellulose, namely D-glucose, D-galactose, L-arabinose, D-xylose and cellobiose. This indicates a possible physiological role of the enzyme in lignocellulose breakdown. PDH showed no detectable activity with oxygen, and its reactivity towards electron acceptors was limited to various substituted benzoquinones and complexed metal ions, with the ferricenium ion and the benzoquinone imine 2,6-dichloroindophenole displaying the highest k(cat)/K-m. The enzyme catalyzed in up to 95% yields the regiospecific conversion of D-galactose to 2-dehydro-D-galactose, an intermediate in a possible biotechnologically interesting process for redox isomerization of D-galactose to the prebiotic sugar D-tagatose. (C) 2007 Elsevier B.V. All rights reserved.
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