Miyazaki Kohji, Hirase Tatsuaki, Kojima Yoichi, Flint Harry James
Laboratory of Animal Science, Kyoto Prefectural University, Shimogamo, Kyoto 606-8522, Japan.
Rowett Research Institute, Bucksburn, Aberdeen AB21 9SB, UK.
Microbiology (Reading). 2005 Dec;151(Pt 12):4121-4125. doi: 10.1099/mic.0.28270-0.
Experiments were done to define the nature of the xylan-derived induction signal for xylanase activity, and evaluate which xylanase genes among the three known ones (xynA, xynB and xynC) are induced by the presence of xylan in Prevotella bryantii B(1)4. During the later stages of exponential growth on glucose, addition of 0.05 % water-soluble xylan (WS-X) stimulated xylanase formation within 30 min. Xylose, xylobiose, xylotriose, xylotetraose, xylopentaose, arabinose and glucuronic acid all failed to induce the xylanase activity. An acid-ethanol-soluble fraction of WS-X (approximate degree of polymerization 30) enhanced the activity significantly, whereas the acid-ethanol-insoluble fraction had no effect, unless first digested by the cloned P. bryantii XynC xylanase. These results indicate that medium- to large-sized xylo-oligosaccharides are responsible for induction. The transcription of all three known xylanase genes from P. bryantii was upregulated coordinately by addition of WS-X. There have been relatively few investigations into the regulation of xylanase activity in bacteria, and it appears to be unique that medium- to large-sized xylo-oligosaccharides are responsible for induction.
开展实验以确定木聚糖衍生的木聚糖酶活性诱导信号的性质，并评估在普氏栖粪杆菌B(1)4中，三种已知木聚糖酶基因（xynA、xynB和xynC）中的哪些基因会被木聚糖诱导。在葡萄糖指数生长后期，添加0.05%的水溶性木聚糖（WS-X）可在30分钟内刺激木聚糖酶的形成。木糖、木二糖、木三糖、木四糖、木五糖、阿拉伯糖和葡萄糖醛酸均未能诱导木聚糖酶活性。WS-X的酸乙醇可溶部分（聚合度约为30）显著增强了活性，而酸乙醇不溶部分则无作用，除非先用克隆的普氏栖粪杆菌XynC木聚糖酶进行消化。这些结果表明，中等到大型的木寡糖是诱导的原因。添加WS-X可使普氏栖粪杆菌所有三个已知木聚糖酶基因的转录协同上调。关于细菌中木聚糖酶活性调控的研究相对较少，中等至大型木寡糖作为诱导因素似乎是独一无二的。
