Biely P, Vrsanská M, Krátký Z
Eur J Biochem. 1980;108(1):313-21. doi: 10.1111/j.1432-1033.1980.tb04725.x.
During growth on wood beta-1,4-xylans the yeast Cryptococcus albidus produced at least two enzymes which convert the polysaccharide to xylose catabolized by the cells. The enzyme almost completely secreted into culture fluid was identified as an endo-1,4-beta-xylanase. The function of the extracellular beta-xylanase is to hydrolyze xylan to oligosaccharides, mainly to xylobiose and xylotriose, which enter the cell where they are split by the second identified enzyme, a cell-bound beta-xylosidae (xylobiase). Aryl beta-xylosidase activity detected in the culture fluid was snown to be due to low affinity of beta-xylanase for p-nitrophenyl beta-D-xylopyranoside. This property of beta-xylanase was preserved after purification of the enzyme by chromatography on DEAE-cellulose, CM-Sephadex and Biogel A 1.5 m or Biogel P 100. Purified beta-xylanase exhibited certain microheterogeneity after polyacrylamide gel electrophoresis. Both extracellular beta-xylanase and intracellular beta-xylosidase were produced in much lower amounts by the cells grown on glucose than by the cells grown on xylan. This suggested that they are not produced constitutively. The investigated strain was not able to grow on cellulose and the crude and purified beta-xylanase were unable to hydrolyze cellulose or its soluble derivatives.
在以木聚糖为碳源生长期间，白色隐球酵母产生了至少两种酶，这些酶可将多糖转化为细胞可分解代谢的木糖。几乎完全分泌到培养液中的酶被鉴定为内切-1,4-β-木聚糖酶。细胞外β-木聚糖酶的功能是将木聚糖水解为寡糖，主要是木二糖和木三糖，这些寡糖进入细胞后被第二种已鉴定的酶（一种细胞结合的β-木糖苷酶（木二糖酶））分解。培养液中检测到的芳基β-木糖苷酶活性被证明是由于β-木聚糖酶对对硝基苯基β-D-吡喃木糖苷的低亲和力。在用DEAE-纤维素、CM-葡聚糖凝胶和Biogel A 1.5m或Biogel P 100进行层析纯化该酶后，β-木聚糖酶的这一特性得以保留。纯化后的β-木聚糖酶在聚丙烯酰胺凝胶电泳后表现出一定的微不均一性。与在木聚糖上生长的细胞相比，在葡萄糖上生长的细胞产生的细胞外β-木聚糖酶和细胞内β-木糖苷酶的量要低得多。这表明它们不是组成型产生的。所研究的菌株不能在纤维素上生长，粗制和纯化的β-木聚糖酶也不能水解纤维素或其可溶性衍生物。
