利用天蓝色链霉菌转化7-木糖紫杉烷的研究

紫杉醇是目前临床治疗癌症的一线化疗药物,资源紧张,价格昂贵。7-木糖-10-去乙酰基紫杉醇(7-XDT)在红豆杉中含量可达紫杉醇的10倍,脱除木糖基后生成的10-脱乙酰紫杉醇(10-DAT)经乙酰化可生成紫杉醇。通过木聚糖平板对不同菌株进行筛选,从52株供试微生物中,发现27株在木聚糖平板上生长良好。经转化实验筛选,发现一株天蓝色链霉菌(Streptomyces coelicolor YUCM 410115)具有转化7-XDT为10-脱乙酰紫杉醇的能力。菌体细胞经破碎离心后,沉淀及上清液均无转化反应出现,而发酵液的硫酸铵沉淀物则可以转化7-XDT生成10-DAT,表明该菌株能产生一种胞外紫杉醇-7-木糖苷酶,发酵液酶活为6 268U。首次发现天蓝色链霉菌能够产生紫杉醇-7-木糖苷酶,为7-XDT转化生产紫杉醇提供了新的酶源。

Study on Transforming 7-xyloyl-taxane by Streptomyces coelicolor

Paclitaxel is currently the first-line drugs in clinical treatment of cancer with strained resources and expensive price.Taxus is rich in 7-xylose-10-deacetylpaclitaxel(7-XDT) of which content is often up to 10 times of paclitaxel.After removal of its xylose group,the product,10-deacetylpaclitaxel(10-DAT)can generate paclitaxel by acetylation.Screened by xylan plates,27 strains could grow on xylan plates from 52 tested strains.A strain of Streptomyces coelicolor YUCM 410115 was first discovered which could produce 10-deacetylpaclitaxel from 7-XDT by transforming test.After cells were broken and centrifuged,there was no transforming reaction in precipitate and supernatant,transforming reaction occurred in the ammonium sulfate precipitation of the fermentation broth.The result showed that the strain could secrete a exo-cellular taxane-7-xylosidase.Enzyme acitivity in fermentation broth was 6 286U.This is a first report about taxane-7-xylosidase secreted by S.coelicolor which provides a new enzyme for transforming 7-XDT.