Two-way traffic of glycoside hydrolase family 18 processive chitinases on crystalline chitin
Two-way traffic of glycoside hydrolase family 18 processive chitinases on crystalline chitin
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DOI：
10.1038/ncomms4975
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发表时间：
2014-06-01
影响因子：
16.6
通讯作者：
Samejima, Masahiro
中科院分区：
文献类型：
--
作者：
Igarashi, Kiyohiko;Uchihashi, Takayuki;Samejima, Masahiro
合成能力是指合成、修饰和降解酶催化与聚合物底物的多个连续反应循环而不从底物脱离的能力。由于生物质多糖，如甲壳素和纤维素，通常形成半结晶区，它们的降解高度依赖于降解酶的持续合成能力。在这里，我们采用高速原子力显微镜直接可视化两个进行性糖苷水解酶家族18几丁质酶（ChiA和ChiB）从几丁质分解细菌粘质沙雷氏菌结晶β-几丁质的运动。进行性运动的半衰期和速度的ChiA是大于那些ChiB，这表明不对称的亚位点结构决定了结晶多糖的进行性降解的方向和幅度。观察到ChiA和ChiB的进行性运动方向相反。双向交通的分子机制进行了讨论，包括与纤维素分解系统的进行性纤维二糖水解酶的比较。
Processivity refers to the ability of synthesizing, modifying and degrading enzymes to catalyse multiple successive cycles of reaction with polymeric substrates without disengaging from the substrates. Since biomass polysaccharides, such as chitin and cellulose, often form recalcitrant crystalline regions, their degradation is highly dependent on the processivity of degrading enzymes. Here we employ high-speed atomic force microscopy to directly visualize the movement of two processive glycoside hydrolase family 18 chitinases (ChiA and ChiB) from the chitinolytic bacterium Serratia marcescens on crystalline beta-chitin. The half-life of processive movement and the velocity of ChiA are larger than those of ChiB, suggesting that asymmetric subsite architecture determines both the direction and the magnitude of processive degradation of crystalline polysaccharides. The directions of processive movements of ChiA and ChiB are observed to be opposite. The molecular mechanism of the two-way traffic is discussed, including a comparison with the processive cellobiohydrolases of the cellulolytic system.