STUDIES OF THE ACTION PATTERN ON POTATO STARCH OF THE DECYCLING MALTODEXTRINASE FROM FLAVOBACTERIUM SP NO-92

The action pattern on potato starch of the decycling maltodextrinase from Flavobacterium sp. no. 92 was studied, and its limit dextrins were analysed. The enzymic activity of the maltodextrinase with starch and its components (1% solutions) proved to be in the order amylose > whole starch >> amylopectin. Revealed by the Michaelis constant of 9 g.L(-1), the enzyme displayed a fairly low affinity for starch, but the maximum hydrolysis rate was found to be around 165 U/mg of protein. The initial products of starch degradation comprised, besides some maltotriose to maltopentaose, mainly maltose, which originated predominantly from amylose, whereas glucose was the main product of amylopectin hydrolysis. The degradation proceeded through a mainly exe-attack in a faster stage, but, in a slower stage, interior chains were broken in an endo-manner as well. Employing high concentrations of enzyme and prolonged incubation, the intermediate larger fragments were hydrolysed to give glucose, maltose, some panose/isopanose, and larger amounts of a branched tetrasaccharide that was probably 6(2)-O-alpha-D-glucosylmaltotriose. The branched saccharides contained all the branch points of the starch and were the limit dextrins of the maltodextrinase. Intermediate larger fragments with a ($) over bar dp of 48, amounting to roughly 27% of amylopectin, and comprising highly branched clusters, were analysed by debranching with pullulanase. Based on the chain profile of the debranched compound, the average structure was evaluated.