Novozymes Inc., Davis, CA 95618, USA.
Bioresour Technol. 2010 Apr;101(7):2405-11. doi: 10.1016/j.biortech.2009.11.057. Epub 2009 Dec 14.
Endoglucanases are important enzymes for biomass conversion and other industrial processes. Determining the specificity of endoglucanases from various glycoside hydrolase families is of interest for bioinformatic functional prediction and substrate-tailored enzyme development. To do so, we characterized approximately 30 endoglucanases from six glycoside hydrolase families. For p-nitrophenyl cellobioside and lactoside, only family 7 enzymes showed significant activity. For xyloglucan, both family 7 and 12 enzymes showed significant activity. For xylan and arabinoxylan, only family 7 enzymes showed significant activity. For mannan and galactomannan, both family 5 and 9 enzymes showed significant activity. The difference in specificity was preliminarily attributed mainly to the structural difference of the enzymes' active sites. For family 7 endoglucanases, difference in thermal stability might affect their performance in hydrolyzing various (hemi)cellulose substrates. Phylogenetic analysis on the subfamily distribution of family 5 endoglucanases (in relation with mannanases) suggested that their mannanase side-activity might be the remnant of an ancestral multi-function enzyme. Similar analysis was also made with the xyloglucanase or arabionxylans side-activity of family 12 and 7 endoglucanases. The apparent dependence of the specificity on family (primary/tertiary structure) might assist us in better understanding the structure-function relationship of the enzymes, and developing more versatile biocatalysts for the utilization of biomass.
内切葡聚糖酶是生物质转化和其他工业过程中的重要酶。确定来自各种糖苷水解酶家族的内切葡聚糖酶的特异性对于生物信息学功能预测和底物定制酶的开发很有意义。为此，我们对来自六个糖苷水解酶家族的大约 30 种内切葡聚糖酶进行了表征。对于对硝基苯基纤维二糖和乳糖，只有家族 7 的酶表现出显著的活性。对于木葡聚糖，家族 7 和 12 的酶都表现出显著的活性。对于木聚糖和阿拉伯木聚糖，只有家族 7 的酶表现出显著的活性。对于甘露聚糖和半乳甘露聚糖，家族 5 和 9 的酶都表现出显著的活性。特异性的差异主要归因于酶活性部位的结构差异。对于家族 7 内切葡聚糖酶，热稳定性的差异可能会影响它们在水解各种（半）纤维素底物方面的性能。对家族 5 内切葡聚糖酶（与甘露聚糖酶有关）亚家族分布的系统发育分析表明，它们的甘露聚糖酶侧活性可能是祖先多功能酶的残余。对家族 12 和 7 内切葡聚糖酶的木葡聚糖酶或阿拉伯木聚糖侧活性也进行了类似的分析。特异性明显依赖于家族（一级/三级结构），这可能有助于我们更好地理解酶的结构-功能关系，并开发更通用的生物催化剂，以利用生物质。
