Roy N, Okai N, Tomita T, Muramoto K, Kamio Y
Laboratory of Applied Microbiology, Tohoku University Graduate School of Agricultural Science, Sendai, Japan.
Biosci Biotechnol Biochem. 2000 Feb;64(2):408-13. doi: 10.1271/bbb.64.408.
Aeromonas caviae W-61 produces multiple extracellular xylanases, the xylanases 1, 2, 3, 4, and 5 [Nguyen, V. D. et al., Biosci. Biotechnol. Biochem., 56, 1708-1712 (1993)]. Here we purified and characterized high-molecular-weight xylanases, the xylanases 4 and 5 from the culture fluids of the bacterium. The purified xylanases 4 and 5, which had molecular masses of 120 and 140 kDa, respectively, were endo-beta-1,4-xylanases with similar enzymatic properties except for trans-xylosidase activity. The xylanase 4 showed a prominent transxylosidase activity when xylotriose and xylotetraose were used as the substrates, while the xylanase 5 had little transxylosidase activity under the same conditions. Protein sequencing indicated that the xylanase 4 was a C-terminally-truncated xylanase 5, suggesting that the C-terminal truncation of the xylanase 5 may endow the enzyme with transxylosidase activity.
豚鼠气单胞菌W-61能产生多种胞外木聚糖酶，即木聚糖酶1、2、3、4和5[阮，V.D.等人，《生物科学、生物技术与生物化学》，56，1708 - 1712(1993)]。在此，我们从该细菌的培养液中纯化并鉴定了高分子量木聚糖酶，即木聚糖酶4和5。纯化后的木聚糖酶4和5，分子量分别为120 kDa和140 kDa，是内切β-1,4-木聚糖酶，除转木糖苷酶活性外，具有相似的酶学性质。当以木三糖和木四糖为底物时，木聚糖酶4表现出显著的转木糖苷酶活性，而在相同条件下木聚糖酶5几乎没有转木糖苷酶活性。蛋白质测序表明木聚糖酶4是C端截短的木聚糖酶5，这表明木聚糖酶5的C端截短可能赋予该酶转木糖苷酶活性。
