Characterization of a thermophilic 4-O-β-D-mannosyl-D-glucose phosphorylase from Rhodothermus marinus
Characterization of a thermophilic 4-O-β-D-mannosyl-D-glucose phosphorylase from Rhodothermus marinus
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DOI：
10.1080/09168451.2014.882760
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发表时间：
2014-02-01
影响因子：
1.6
通讯作者：
Mori, Haruhide
中科院分区：
文献类型：
--
作者：
Jaito, Nongluck;Saburi, Wataru;Mori, Haruhide
4-O-β-D-甘露糖基-D-葡萄糖磷酸化酶（MGP），发现于厌氧菌中，将4-O-β-D-甘露糖基D-葡萄糖（Man-Glc）转化为α-D-甘露糖基磷酸和D-葡萄糖。它与纤维二糖2-差向异构酶（CE）一起参与甘露聚糖代谢，后者将β-1，4-甘露二糖转化为Man-Glc。一个推定的MGP基因存在于嗜热需氧菌Rhodothermus marinus（Rm）的基因组中编码CE的基因上游。魔芋葡甘聚糖提高了R. marinus的MGP、CE和胞外甘露聚糖内切-1，4-β-甘露糖苷酶。重组RmMGP通过涉及三元复合物形成的连续双-双机制催化Man-Glc的磷酸解。在变性和非变性条件下，其分子量分别为45和222 kDa。其最适pH和温度为6.5和75 ℃，在pH 5.5-8.3和80 ℃以下稳定。在逆反应中，RmMGP对6-脱氧-D-葡萄糖和D-木糖的受体选择性高于R。albus NE1 MGP.与R. albus NE 1 MGP、RmMGP利用甲基β-D-葡萄糖苷和1，5-脱水-D-葡萄糖醇作为受体底物。
4-O-beta-D-Mannosyl-D-glucose phosphorylase (MGP), found in anaerobes, converts 4-O-beta-D-mannosylD- glucose (Man-Glc) to alpha-D-mannosyl phosphate and D-glucose. It participates in mannan metabolism with cellobiose 2-epimerase (CE), which converts beta-1,4-mannobiose to Man-Glc. A putative MGP gene is present in the genome of the thermophilic aerobe Rhodothermus marinus (Rm) upstream of the gene encoding CE. Konjac glucomannan enhanced production by R. marinus of MGP, CE, and extracellular mannan endo-1,4-beta-mannosidase. Recombinant RmMGP catalyzed the phosphorolysis of Man-Glc through a sequential bi-bi mechanism involving ternary complex formation. Its molecular masses were 45 and 222 kDa under denaturing and nondenaturing conditions, respectively. Its pH and temperature optima were 6.5 and 75 degrees C, and it was stable between pH 5.5-8.3 and below 80 degrees C. In the reverse reaction, RmMGP had higher acceptor preferences for 6-deoxy-D-glucose and D-xylose than R. albus NE1 MGP. In contrast to R. albus NE1 MGP, RmMGP utilized methyl beta-D-glucoside and 1,5-anhydro- D-glucitol as acceptor substrates.