Cyclodextrin glycosyltransferase variants experience different modes of product inhibition

Cyclodextrin glycosyltransferase (CGTase) can be used for the industrial production of cyclodextrins. However, product inhibition by cyclodextrins largely restrains the cyclization activities of CGTase and severely limits the application of cyclodextrins. In this paper, the kinetic mechanisms of the three kinds of cyclization reaction were studied, and the product inhibition modes of two CGTases from different sources were compared. The results confirm that the synthesis of each cyclodextrin is substantially inhibited by the corresponding cyclodextrin. Meanwhile, product inhibition studies indicate competitive inhibition for α-CGTase and a mixed pattern for β-CGTase. This demonstrates that the inhibition type is not decided by the kinds of cyclodextrins or the varieties of cyclization reactions, but by the structure of the CGTase.