The role of domain E in the activity of Bacillus macerans cyclodextrin glucanotransferase

摘要: Cyclodextrin glucanotransferase (CGT) is an industrial enzyme used for the production of cyclodextrins (CDs). CGT folds into five domains A, B, C, D and E. Domain E has ability to bind starch (CDs) considered starch-binding domain CGT. Two maltose binding sites (MBS1 MBS2) have been identified in participates formation a deep groove which located on protein surface extends from active site MBS2. To investigate function catalysis CGT, mutants were constructed using Bacillus macerans. The truncated (CGTAE), was by deleting In chimeric (CGT-SBD), replaced with (SBD) glucoamylase I (GAI), similar structure modified (CGT+6) inserting six amino acids between inserted as pseudo linker order perturb alignment increasing distance CGTAE exhibited no detectable activity, whereas CGT-SBD had very low cyclization, starch-degrading, coupling activities. CGT+6 about 5060% wild type (WT-CGT) its thennostability lower than that WT-CGT. K^, value cyclization activity 2.6 fold greater efficiency reaction (kgat /K„) also significantly reduced.