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Cyclodextrin glycosyltransferases (CGTases) from Paenibacillus macerans, Thermoanaerobacter sp. ATCC 53627, Bacillus stearothermophilus and a Carboxydocella sp. (phylogenetically identified from genomic DNA) were characterized with respect to their catalytic activity in different reactions, with emphasis on reactions useful for the elongation of the carbohydrate group of alkyl glycosides. All CGTases had activities between 95 and 115 U/mg in the coupling reaction between α-cyclodextrin (α-CD) as glucosyl donor and β-dodecyl maltoside as glucosyl acceptor, but differed very much in the competing hydrolysis of α-CD. The α-CD hydrolysis activity ranged from 0.13 U/mg for P. macerans CGTase to 10.5 U/mg for the Carboxydocella sp. (CspCGT13). Furthermore, the disproportionation activity was much lower for the Paenibacillus CGTase compared to the other CGTases, and consequently this enzyme …