title: Mutations at subsite -3 in cyclodextrin glycosyltransferase from Paenibacillus macerans enhancing alpha-cyclodextrin specificity.
abstract: A major disadvantage of cyclodextrin production is the limited cyclodextrin product specificity of cyclodextrin glycosyltransferase (CGTase). Here, we described mutations of Asp372 and Tyr89 at subsite -3 in the CGTase from Paenibacillus macerans strain JFB05-01. The results showed that Asp372 and Tyr89 played important roles in cyclodextrin product specificity of CGTase. The replacement of Asp372 by lysine and Tyr89 by aspartic acid, asparagine, lysine, and arginine resulted in a shift in specificity towards the production of alpha-cyclodextrin, which was most apparent for the mutants D372K and Y89R. Furthermore, the changes in cyclodextrin product specificity for the single mutants D372K and Y89R could be combined in the double mutant D372K/Y89R, which displayed a 1.5-fold increase in the production of alpha-cyclodextrin, with a concomitant 43% decrease in the production of beta-cyclodextrin when compared to the wild-type CGTase. Thus, the D372K and Y89R single and double mutants were much more suitable for the industrial production of alpha-cyclodextrin than the wild-type enzyme. The enhanced alpha-cyclodextrin specificity of these mutants might be a result of stabilizing the bent conformation of the intermediate in the cyclization reaction.
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, 1800 Lihu Ave., Wuxi 214122, People's Republic of China.
authors.forename: Zhaofeng
authors.initials: Z
authors.lastname: Li
authors.forename: Jiayu
authors.initials: J
authors.lastname: Zhang
authors.forename: Miao
authors.initials: M
authors.lastname: Wang
authors.forename: Zhengbiao
authors.initials: Z
authors.lastname: Gu
authors.forename: Guocheng
authors.initials: G
authors.lastname: Du
authors.forename: Jianke
authors.initials: J
authors.lastname: Li
authors.forename: Jing
authors.initials: J
authors.lastname: Wu
authors.forename: Jian
authors.initials: J
authors.lastname: Chen
mesh_terms: D001407:Bacillus / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D001665:Binding Sites; D005964:Glucosyltransferases / Q000737:chemistry* / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D013379:Substrate Specificity; D047391:alpha-Cyclodextrins / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D047391:alpha-Cyclodextrins; D005964:Glucosyltransferases; C019963:cyclomaltodextrin glucanotransferase; C032613:alpha-cyclodextrin