Sygmund Christoph, Kittl Roman, Volc Jindrich, Halada Petr, Kubátová Elena, Haltrich Dietmar, Peterbauer Clemens K
Division of Food Biotechnology, Department of Food Sciences and Technology, BOKU - University of Natural Resources and Applied Life Sciences, A-1190 Vienna, Austria.
J Biotechnol. 2008 Feb 1;133(3):334-42. doi: 10.1016/j.jbiotec.2007.10.013. Epub 2007 Nov 9.
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 66,547Da as determined by matrix-assisted laser desorption/ionisation mass spectrometry containing approximately 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.
从姬松茸的菌丝体培养基中，利用离子交换色谱法和疏水相互作用色谱法，将其吡喃糖脱氢酶（PDH）纯化至基本均一。通过基质辅助激光解吸/电离质谱法测定，天然酶是一种单体多肽，分子量为66,547Da，含有约7%的碳水化合物和共价结合的黄素腺嘌呤二核苷酸。该酶表现出广泛的糖底物耐受性，能将不同的醛吡喃糖氧化为相应的C-2或C-2,3（二）脱氢糖。具有最高k(cat)/K(m)值的优选电子供体是纤维素和半纤维素的主要糖成分，即D-葡萄糖、D-半乳糖、L-阿拉伯糖、D-木糖和纤维二糖。这表明该酶在木质纤维素分解中可能具有生理作用。PDH对氧气无检测到的活性，其对电子受体的反应性仅限于各种取代的苯醌和络合金属离子，其中三价铁离子和苯醌亚胺2,6-二氯靛酚表现出最高的k(cat)/K(m)。该酶以高达95%的产率催化D-半乳糖区域特异性转化为2-脱氢-D-半乳糖，这是D-半乳糖氧化还原异构化为益生元糖D-塔格糖的一个可能具有生物技术意义的过程中的中间体。
