来源于橄榄绿链霉菌（Streptomyces olivaceoviridis）A1的木聚糖酶XYNB是一性质优良的高比活性木聚糖酶，已在饲料中作为添加剂应用。本研究利用携带双35S启动子和AMV增强子的表达载体，在烟草中高效表达了XYNB。转基因烟草及其子代植株基因组PCR检测证实xynB基因已整合到转基因烟草的基因组中, ELISA和SDS-PAGE以及Western blotting分析确证了xynB基因的高效表达, 木聚糖酶活性分析证实了表达酶具有正常的生物学活性。表达的XYNB约占叶片总蛋白含量的6%， 转基因烟草表现的最高酶活性约为170 IU/g鲜叶片(23 IU/mg总蛋白)。表达酶蛋白分子量为20.8 kD, 与理论分子量相当。转基因植株可以正常生长和繁殖，T1子代植株表现了与亲代相似的酶活性，具有较好的遗传稳定性。
The gene encoding XYNB with high specific activity from Streptomyces olivaceoviridis A1 was expressed in tobacco plant under the control of an efficient double 35S promoter and AMV enhancer. The integration of the xynB in the genome of tobacco was confirmed by PCR detection of T0 and T1 plants. ELISA, SDS-PAGE and Western blot analysis confirmed the presence of XYNB enzyme. High levels of the 20.8 kD protein(Fig.4 and Fig.5)，which was as same as that of original xylanase (XYNB)， was synthesized in cytoplasm or targeted to the intercellular space by means of the potato proteinase inhibitorⅡ signal peptide. The recombinant xylanase was accumulated to the level of up to 6% of total soluble leaf proteins. And in transgenic leaf tissues, xylanase activity up to 170 IU/g fresh leaf (23 IU·mg-1 total protein) was observed. Furthermore, growth and development of the transgenic plants was not affected by the expression of foreign enzyme, and T1 plants showed the genetic stability. The results demonstrated that transgenic plants can be used to produce high activity recombinant xylanase efficiently, and can be as the alternative of custom feed additives.
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