Industrial Bio-materials Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon 305-806, Republic of Korea.
Enzyme Microb Technol. 2011 Apr 7;48(4-5):365-70. doi: 10.1016/j.enzmictec.2010.12.013. Epub 2011 Jan 12.
A xylanolytic gut bacterium isolated from Eisenia fetida, Cellulosimicrobium sp. strain HY-13, produced an extracellular glycoside hydrolase capable of efficiently degrading mannose-based substrates such as locust bean gum, guar gum, mannotetraose, and mannopentaose. The purified mannan-degrading enzyme (ManK, 34,926 Da) from strain HY-13 was found to have an N-terminal amino acid sequence of DEATTDGLHVVDD, which has not yet been identified. Under the optimized reaction conditions of 50°C and pH 7.0, ManK exhibited extraordinary high specific activities of 7109 IU/mg and 5158 IU/mg toward locust bean gum and guar gum, respectively, while the enzyme showed no effect on sugars substituted with p-nitrophenol and various non-mannose carbohydrates. Thin layer chromatography revealed that the enzyme degraded locust bean gum to mannobiose and mannotetraose. No detectable amount of mannose was produced from hydrolytic reactions with the substrates. ManK strongly attached to Avicel, β-cyclodextrin, lignin, and poly(3-hydroxybutyrate) granules, but not bound to chitin, chitosan, curdlan, or insoluble oat spelt xylan. The aforementioned characteristics of ManK suggest that it is a unique endo-β-1,4-mannanase without additional carbohydrolase activities, which differentiates it from other well-known carbohydrolases.
从赤子爱胜蚓中分离得到的木聚糖降解肠道细菌，即纤维微菌属 HY-13 菌株，产生了一种能够有效降解甘露糖基底物的胞外糖苷水解酶，如胡芦巴胶、瓜尔胶、甘露四糖和甘露五糖。从 HY-13 菌株中纯化出的甘露聚糖降解酶（ManK，34926 Da）具有一个未被鉴定的 N-末端氨基酸序列 DEATTDGLHVVDD。在 50°C 和 pH 7.0 的优化反应条件下，ManK 对胡芦巴胶和瓜尔胶的比活性分别高达 7109 IU/mg 和 5158 IU/mg，而该酶对带有对硝基苯酚和各种非甘露糖碳水化合物取代的糖没有影响。薄层色谱显示该酶将胡芦巴胶降解为甘露二糖和甘露四糖。在水解反应中没有检测到来自底物的甘露糖。ManK 强烈附着在微晶纤维素、β-环糊精、木质素和聚（3-羟基丁酸酯）颗粒上，但不与几丁质、壳聚糖、普鲁兰或不溶性燕麦黑麦木聚糖结合。ManK 的上述特性表明它是一种独特的内切-β-1,4-甘露聚糖酶，没有额外的碳水化合物酶活性，这使其与其他知名的碳水化合物酶区分开来。
