Purification and characterization of a cyclodextrin-degrading enzyme from Flavobacterium sp.

A cell-bound cyclodextrin-degrading enzyme with a relative molecular mass (M_r) of around 62 000 and an isoelectric point (pI) near 8.0 was isolated and purified to 94% homogeneity from Flavobacterium sp. The enzyme hydrolysed maltooligosaccharides and cyclodextrins to glucose, maltose, and maltotriose. Less glucose, but larger amounts of the line of maltooligosaccharides from maltose to (in case of cyclodextrins) the linearized substrates were found in short-term digests. Digestion of maltotriose yielded glucose, maltose, and some maltotetraose to maltohexaose, i.e. the enzyme catalysed both hydrolysis and transglycosylation. Starch was a poorer substrate, and was hydrolysed to mainly glucose and maltose, presumably by a kind of exo-attack. Pullulan was slightly digested, the products being glucose, panose/isopanose, and larger saccharides containing -1,6-glucosidic bonds. Since maltohexaose to maltooctaose were hydrolysed at higher rates than the cyclodextrins of corresponding lengths, the enzyme of Flavobacterium sp. was proposed to be classified as a decycling maltodextrinase.Correspondence to: H. Bender