[Kinetic studies of the (1 linked to 4)-alpha-D-glucopyranosyltransferase reaction catalyzed by cyclodextrin glycosyltransferase, particularly the cyclization with (1 linked to 4)-alpha-D-glucopyranosyl chains (average polymerization of 16) as substrate]

The transfer reactions, particularly the cyclization reaction, catalyzed by the cyclodextrin glycosyltransferase ((1 leads to 4)-alpha-D-glucan:[(1 leads to 4)-alpha-D-glucopyranosyl]-transferase (cyclizing), EC 2.4.1.19; CGT) from Klebsiella pneumoniae M 5 al were studied with (1 leads to 4)-alpha-D-glucopyranosyl chains (d.p. 16). The initial rate of the cyclization reaction with substrate concentrations from 1 up to 16 mM indicated a V of 6.2 kat . kg-1 of protein and a molar catalytical activity of 421.6 kat . mol-1 of enzyme. Km was found to be 1.03 mM. In addition to the cyclization, CGT simultaneously catalyzed a disproportionation of the substrate, yielding shorter maltooligosaccharides and (1 leads to 4)-alpha-D-glucopyranosyl chains which were significantly longer than the substrate itself. Cyclohepta- and cycloocta-amylose were accumulated in the course of longer incubation. They arose mainly from coupling reactions with the initially formed cyclohexaamylose and corresponding disproportionation of these transfer products. The extremely low formation rates of the higher cyclodextrins point to a "mistake" of the enzyme, when cyclizing to cyclohepta- and cyclooctaamylose.