摘要
Squalene and oxidosqualene cyclizations are regarded as the most complex chemical reactions in the nature,which can achieve protonation,deprotonation,a sequence of hydride and methyl migration. Dammarenediol-Ⅱ synthase（ DS）,as a kind of 2,3-oxidosqualene-triterpene cyclase,catalyses2,3-oxidosqualene to form dammarenediol-Ⅱ. To assess the three-dimensional（ 3 D） structure and catalytic active sites of dammarenediol-Ⅱ synthase,utilizing the homology modeling method,3 D models of DS were established in the Modeller9 v14 software and I-TASSER server. With the highest sequence identity with DS,human oxidosqualene cyclase 3 D models（ PDB： 1 W6K and 1 W6J） were chosen as templates. Through further evaluation and optimization,an optimal DS model was obtained consequently. Then several putative catalytic active sites were found through the molecular docking simulation between DS model and product dammarenediol-Ⅱ by using Autodock 4. 2. Finally,site-directed mutants of DS were expressed in Saccharomyces cerevisiae,a significant decrease of the yield of dammarenediol-Ⅱ is achieved,which verified the significance of these putative active sites.
Squalene and oxidosqualene cyclizations are regarded as the most complex chemical reactions in the nature,which can achieve protonation,deprotonation,a sequence of hydride and methyl migration. Dammarenediol-Ⅱ synthase（ DS）,as a kind of 2,3-oxidosqualene-triterpene cyclase,catalyses2,3-oxidosqualene to form dammarenediol-Ⅱ. To assess the three-dimensional（ 3 D） structure and catalytic active sites of dammarenediol-Ⅱ synthase,utilizing the homology modeling method,3 D models of DS were established in the Modeller9 v14 software and I-TASSER server. With the highest sequence identity with DS,human oxidosqualene cyclase 3 D models（ PDB： 1 W6K and 1 W6J） were chosen as templates. Through further evaluation and optimization,an optimal DS model was obtained consequently. Then several putative catalytic active sites were found through the molecular docking simulation between DS model and product dammarenediol-Ⅱ by using Autodock 4. 2. Finally,site-directed mutants of DS were expressed in Saccharomyces cerevisiae,a significant decrease of the yield of dammarenediol-Ⅱ is achieved,which verified the significance of these putative active sites.
基金
Supported by the National Basic Research Program of China(2012CB721105)
the Major Research Plan of Tianjin(16YFXTSF00460)
