Centre of Molecular and Environmental Biology (CBMA)/Aquatic Research Network (ARNET), Department of Biology, University of Minho, 4710-057 Braga, Portugal; Institute of Science and Innovation for Sustainability (IB-S), University of Minho, Gualtar Campus, 4710-057 Braga, Portugal.
Centre of Molecular and Environmental Biology (CBMA)/Aquatic Research Network (ARNET), Department of Biology, University of Minho, 4710-057 Braga, Portugal; Institute of Science and Innovation for Sustainability (IB-S), University of Minho, Gualtar Campus, 4710-057 Braga, Portugal.
Biotechnol Adv. 2023 Jul-Aug;65:108148. doi: 10.1016/j.biotechadv.2023.108148. Epub 2023 Apr 7.
Endo-1,4-β-xylanases (EC 3.2.1.8) are O-glycoside hydrolases that cleave the internal β-1,4-D-xylosidic linkages of the complex plant polysaccharide xylan. They are produced by a vast array of organisms where they play critical roles in xylan saccharification and plant cell wall hydrolysis. They are also important industrial biocatalysts with widespread application. A large and ever growing number of xylanases with wildly different properties and functionalites are known and a better understanding of these would enable a more effective use in various applications. The Carbohydrate-Active enZYmes database (CAZy), which classifies evolutionarily related proteins into a glycoside hydrolase family-subfamily organisational scheme has proven powerful in understanding these enzymes. Nevertheless, ambiguity currently exists as to the number of glycoside hydrolase families and subfamilies harbouring catalytic domains with true endoxylanase activity and as to the specific characteristics of each of these families/subfamilies. This review seeks to clarify this, identifying 9 glycoside hydrolase families containing enzymes with endo-1,4-β-xylanase activity and discussing their properties, similarities, differences and biotechnological perspectives. In particular, substrate specificities and hydrolysis patterns and the structural determinants of these are detailed, with taxonomic aspects of source organisms being also presented. Shortcomings in current knowledge and research areas that require further clarification are highlighted and suggestions for future directions provided. This review seeks to motivate further research on these enzymes and especially of the lesser known endo-1,4-β-xylanase containing families. A better understanding of these enzymes will serve as a foundation for the knowledge-based development of process-fitted endo-1,4-β-xylanases and will accelerate their development for use with even the most recalcitrant of substrates in the biobased industries of the future.
内切-1,4-β-木聚糖酶（EC 3.2.1.8）是 O-糖苷水解酶，能够切割复杂植物多糖木聚糖的内部β-1,4-D-木糖苷键。它们由大量生物产生，在木聚糖糖化和植物细胞壁水解中发挥关键作用。它们也是具有广泛应用的重要工业生物催化剂。目前已知具有广泛不同性质和功能的大量内切-1,4-β-木聚糖酶，对这些酶的更好理解将使它们在各种应用中更有效地使用。碳水化合物活性酶数据库（CAZy）将进化相关的蛋白质分类为糖苷水解酶家族-亚家族组织方案，已被证明在理解这些酶方面非常有效。然而，目前仍然存在歧义，即有多少糖苷水解酶家族和亚家族含有具有真正内切-1,4-β-木聚糖酶活性的催化结构域，以及这些家族/亚家族的每个家族/亚家族的具体特征。本综述旨在阐明这一点，确定了 9 个含有具有内切-1,4-β-木聚糖酶活性的酶的糖苷水解酶家族，并讨论了它们的性质、相似性、差异和生物技术前景。特别是详细说明了它们的底物特异性、水解模式和结构决定因素，同时还介绍了来源生物的分类学方面。突出了当前知识的不足之处和需要进一步澄清的研究领域，并提供了未来方向的建议。本综述旨在激发对这些酶的进一步研究，特别是对鲜为人知的含有内切-1,4-β-木聚糖酶的家族的研究。对这些酶的更好理解将为基于知识的过程适配内切-1,4-β-木聚糖酶的开发奠定基础，并加速它们在未来生物基工业中即使是最顽固的底物的开发和应用。
