Altered product specificity of a cyclodextrin glycosyltransferase by molecular imprinting with cyclomaltododecaose

Cyclodextrin glycosyltransferases (CGTases), members of glycoside hydrolase family 13, catalyze the conversion of amylose to cyclodextrins (CDs), circular alpha-(1,4)-linked glucopyranose oligosaccharides of different ring sizes. The CD containing 12 alpha-D-glucopyranose residues was preferentially synthesized by molecular imprinting of CGTase from Paenibacillus sp. A11 with cyclomaltododecaose (CD(12)) as the template molecule. The imprinted CGTase was stabilized by cross-linking of the derivatized protein. A high proportion of CD(12) and larger CDs was obtained with the imprinted enzyme in an aqueous medium. The molecular imprinted CGTase showed an increased catalytic efficiency of the CD(12)-forming cyclization reaction, while decreased k(cat)/K(m) values of the reverse ring-opening reaction were observed. The maximum yield of CD(12) was obtained when the imprinted CGTase was reacted with amylose at 40 degrees C for 30 min. Molecular imprinting proved to be an effective means toward increase in the yield of large-ring CDs of a specific size in the biocatalytic production of these interesting novel host compounds for molecular encapsulations.