Kinetische untersuchungen der durch die cyclodextrin-glycosyltransferase katalysierten (1→4)-β-d-glucopyrano-syltransferreaktionen,insbesondere der zyklisierungs-reaktion,mit (1→4)-α-D-glucopyranosylketten “durchschnittlicher polymerisationsgrad von 16” als substrat

The transfer reactions, particularly the cyclization reaction, catalysed by the cyclodextrin glycosyltransferase {(1→4)-α-D-glucan:(l→4)-α-D-glucopyranosyl]-transferase (cyclizing), EC 2.4.1.19; CGT} from Klebsiella pneumoniae M 5 al were studied with (1→4)-α-D-glucopyranosyl chains (d.p. 16). The initial rate of the cyclization reaction with substrate concentrations from 1 up to 16mM indicated a V of 6.2 kat &∣ kg^-1 of protein and a molar catalytical activity of 421.6 kat &∣ mol^-1 of enzyme. K_m was found to be 1.03mM. In addition to the cyclization, CGT simultaneously catalysed a disproportionation of the substrate, yielding shorter maltooligosaccharides and (1→4)-α-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 cyclooctamylose.