Notario V, Villa T G, Villanueva J R
J Gen Microbiol. 1979 Oct;114(2):415-22. doi: 10.1099/00221287-114-2-415.
1,4-beta-D-Xylanase (1,4-beta-D-xylan xylanohydrolase; EC 3.2.1.8) has been detected in both cell-free extracts and culture fluids of the yeast Cryptococcus albidus var. aerius grown on glucose as the only carbon source. Mild acid treatment of whole cells proved that the enzyme was extracellularly located. The activity remained almost completely linked to the wall after cell breakage, only being liberated in the presence of salt at high concentration. After release, the enzyme became very unstable and so has been characterized in situ in 'permeabilized' cells. The maximum production took place at the beginning of the exponential growth phase. The optimum pH and temperature for activity were 5.0 and 40 degrees C, respectively. The enzyme degraded xylan and xylo-oligosides by an endo-splitting mechanism giving xylobiose, xylotriose and xylose as the main end-products. Activation energy and kinetic constants for xylan degradation were determined. Several metal ions such as Ag+ and Hg2+ inhibited the enzyme. The possible function of this endo-xylanase in Cr. albidus var. aerius is discussed.
在以葡萄糖作为唯一碳源生长的酵母浅白隐球酵母气生变种的无细胞提取物和培养液中均检测到了1,4-β-D-木聚糖酶（1,4-β-D-木聚糖木聚糖水解酶；EC 3.2.1.8）。对完整细胞进行温和酸处理证明该酶位于细胞外。细胞破碎后，酶活性几乎完全与细胞壁相连，只有在高浓度盐存在时才会释放出来。释放后，该酶变得非常不稳定，因此已在“通透化”细胞中原位进行了表征。最大产量出现在指数生长期开始时。该酶活性的最适pH和温度分别为5.0和40℃。该酶通过内切机制降解木聚糖和木寡糖，主要终产物为木二糖、木三糖和木糖。测定了木聚糖降解的活化能和动力学常数。几种金属离子如Ag+和Hg2+抑制该酶。讨论了这种内切木聚糖酶在浅白隐球酵母气生变种中的可能功能。
