Aldopentoses as new substrates for the membrane-bound, pyrroloquinoline quinone-dependent glycerol (polyol) dehydrogenase of Gluconobacter sp.
Aldopentoses as new substrates for the membrane-bound, pyrroloquinoline quinone-dependent glycerol (polyol) dehydrogenase of Gluconobacter sp.
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DOI：
10.1007/s00253-018-8848-1
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发表时间：
2018-02
影响因子：
5
通讯作者：
T. Yakushi;Y. Terada;Seishiro Ozaki;Naoya Kataoka;Y. Akakabe;O. Adachi;Minenosuke Matsutani;K. Matsushita
中科院分区：
文献类型：
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作者：
T. Yakushi;Y. Terada;Seishiro Ozaki;Naoya Kataoka;Y. Akakabe;O. Adachi;Minenosuke Matsutani;K. Matsushita
葡萄糖杆菌的膜结合的依赖于吡咯喹啉醌(PQQ)的甘油脱氢酶(GLDH或多元醇脱氢酶)。氧化各种仲醇以产生相应的酮，例如在维生素C生产中将d-山梨醇氧化为l-山梨糖。GLDH的底物专一性被认为仅限于在倒数第二个碳的红构型中的仲醇。在此，我们认为L-核糖、D-和L-裂解糖以及L-塔格糖也是GLDH的底物，但这些糖不符合GLDH的底物专一性规则。与GLDH阴性变异体的膜相比，野生型葡萄糖杆菌膜的耗氧活性依赖于几种糖。对这些糖与膜的生物转化进行了检测，以确定反应产物。通过测定反应混合物的pH值和薄层色谱上底物和产物的增减，发现L-乳糖和L-塔格糖的氧化产物为结构未知的酮，而L-核糖和D-乳糖的氧化产物为酸。对L-核糖的氧化产物进行了提纯，并通过HRMS和核磁共振分析揭示了其为核糖酸贝勒酯。L-核糖与膜和整个细胞的生物转化生成接近化学计量比的L-核糖，表明L-核糖中的特定氧化位点被GLDH识别。由于纯化的GLDH生成的L-核糖不含任何中间体，因此我们提出了一种反应模型，即用GLDH将L-核糖中的吡喃糖的第一个碳氧化成L-核内酯，再由后者自发水解生成L-核糖酸酯。
Membrane-bound, pyrroloquinoline quinone (PQQ)-dependent glycerol dehydrogenase (GLDH, or polyol dehydrogenase) ofGluconobactersp. oxidizes various secondary alcohols to produce the corresponding ketones, such as oxidation ofD-sorbitol toL-sorbose in vitamin C production. Substrate specificity of GLDH is considered limited to secondary alcohols in theD-erythroconfiguration at the next to the last carbon. Here, we suggest thatL-ribose,D- andL-lyxoses, andL-tagatose are also substrates of GLDH, but these sugars do not meet the substrate specificity rule of GLDH. The oxygen consumption activity of wild-typeGluconobacter frateuriicell membranes depends on several kinds of sugars as compared with that of the membranes of a GLDH-negative variant. Biotransformation of those sugars with the membranes was examined to determine the reaction products. A time course measuring the pH in the reaction mixture and the increase or decrease in substrates and products on TLC suggested that oxidation products ofL-lyxose andL-tagatose were ketones with unknown structures, but those ofL-ribose andD-lyxose were acids. The oxidation product ofL-ribose was purified and revealed to beL-ribonate by HRMS and NMR analysis. Biotransformation ofL-ribose with the membranes and also with the whole cells producedL-ribonate in nearly stoichiometric amounts, indicating that the specific oxidation site inL-ribose is recognized by GLDH. Since purified GLDH producedL-ribonate without any intermediate-like compounds, we propose here a reaction model where the first carbon in the pyranose form ofL-ribose is oxidized by GLDH toL-ribonolactone, which is further hydrolyzed spontaneously to produceL-ribonate.