title: Enzymatic hydrolysis of 7-xylosyltaxanes by an extracellular xylosidase from Cellulosimicrobium cellulans.
abstract: OBJECTIVE
  To find extracellular biocatalysts that can specifically and efficiently remove the C-7 xylosyl group from 7-xylosyltaxanes.
  
  
  RESULTS
  A Cellulosimicrobium cellulans strain F16 that can remove the C-7 xylosyl group from 7-xylosyltaxanes was isolated from the root soil of an old Taxus yunnanensis tree. Using corn cob as sole carbon source, the maximum 7-xylosyl-10-deacetylpaclitaxel β-xylosidase activity of 9.6 U l(-1) was achieved. The β-xylosidase could be trapped by a ceramic tubular membrane (pore size 50 nm), and exhibited an apparent molecular weight much greater than 500 kDa. Under optimized conditions, 3.75 l cell-free culture medium transformed 2 grams 7-xylosyltaxane mixtures to their corresponding aglycones within 3 h, with a conversion >98%.
  
  
  CONCLUSIONS
  This is the first report that C. cellulans can produce extracellular β-xylosidases capable of removing the C-7 xylosyl group from 7-xylosyltaxanes.
authors.affiliation: Laboratory of Pharmaceutical Resource Discovery, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457, Zhongshan Road, Dalian, 116023, Liaoning, People's Republic of China.
authors.forename: Tong-Yi
authors.initials: TY
authors.lastname: Dou
authors.forename: Hong-Wei
authors.initials: HW
authors.lastname: Luan
authors.forename: Xing-Bao
authors.initials: XB
authors.lastname: Liu
authors.forename: Shi-Yang
authors.initials: SY
authors.lastname: Li
authors.forename: Xun-Fu
authors.initials: XF
authors.lastname: Du
authors.forename: Ling
authors.initials: L
authors.lastname: Yang
mesh_terms: D001426:Bacterial Proteins / Q000302:isolation & purification / Q000378:metabolism; D055162:Biocatalysis; D002474:Cell-Free System; D006868:Hydrolysis; D008835:Micrococcaceae / Q000201:enzymology / Q000235:genetics*; D012988:Soil Microbiology; D043823:Taxoids / Q000737:chemistry*; D014995:Xylosidases / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D043823:Taxoids; D014995:Xylosidases; C026579:exo-1,4-beta-D-xylosidase