Cereal Chem 43:111 - 118.  |  VIEW ARTICLE

The Mechanism of Carbohydrase Action. XI. Pullulanase, an Enzyme Specific for the Hydrolysis of Alpha-1-6-Bonds in Amylaceous Oligo- and Polysaccharides.

M. Abdullah, B. J. Catley, E. Y. C. Lee, J. Robyt, K. Wallenfels, and W. J. Whelan. Copyright 1966 by the American Association of Cereal Chemists, Inc. 

Pullulanase, an extracellular enzyme of Aerobacter aerogenes, is specific for the hydrolysis of alpha-1-6- glucosidic linkages in branched amylaceous polysaccharides and derived oligosaccharides. Its action and specificity are closely similar to the plant R-enzyme complex, but pullulanase has the additional capacity to effect a limited degree of hydrolysis of the branch linkages of glycogen, which R-enzyme, for steric reasons, does not. Steric hindrance to pullulanase action on both amylopectin and glycogen does also occur, but is lessened if the outer chains of the polysaccharide are first degraded by beta-amylase. The specificity of pullulanase has been defined by means of exposure to oligosaccharides of known constitution. It does not hydrolyze isomaltose, and there is an absolute requirement for alpha-1-4-glucosidic bonds in its substrates. It has no detectable action on compounds in which alpha-glucose is joined through a 1-6-bond to a maltosaccharide, while its action on alpha-maltosaccharides joined 1-6 to glucose is either negligible or so slow that it could be due to an enzymatic impurity. Pullulanase acts rapidly on alpha-1-6-bonds only when each of the components joined through the linkage is a maltosaccharide. Thus the linear tetra saccharide 6(2)-alpha-maltosylmaltose is the smallest substrate capable of rapid hydrolysis.