木聚糖(xylan)是一种存在于植物细胞壁中的异质多糖，约占植物细胞干重的15%~35%，是植物半纤维素(hemicellose)的主要成分。大多数木聚糖是一种结构复杂的、具有高度分枝的异质多糖，含有许多不同的取代基。木聚糖的生物降解也因此需要一个复杂的酶系统，通过其中各种组分的相互协同作用来降解木聚糖。因此，木聚糖酶是一组酶，而非一种酶。

Xylan (Xylan) is a kind of heterogenous polysaccharide which exists in the plant cell wall. It accounts for about 15% ~ 35% of the dry weight of plant cells and is the main component of hemicellose. Most xylans are complex, highly branched, heterogeneous polysaccharides with many different substituents. Therefore, the biodegradation of Xylan requires a complex enzyme system, through which the interaction of various components to degrade xylan. Therefore, xylanase is a group of enzymes, not an enzyme.