The mechanism of carbohydrase action. 8. Structures of the muscle-phosphorylase limit dextrins of glycogen and amylopectin

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Abstract
The structures of the limit dextrins produced by the action of rabbit-muscle phosphorylase on glycogen and amylopectin were examined by enzymic methods. The formula previously assigned by Cori and Lamer (1951) to the outer chains of the dextrins is incorrect. The side chains are not single glucose units but are probably 4 units long. Correspondingly the outer portions of the main chains are shorter than was supposed. A preparation of amylo-1,6-glucosidase, the enzyme which splits the branch links in the phosphorylase limit dextrins, proved to be contaminated with a transglycosylase, acting on maltodextrins. The presence of this second enzyme may accound for the formation of glucose when the amylo-1,6-glucosidase acts on phosphorylase limit dextrins. The splitting of isomaltose by crude muscle extracts is largely, if not entirely, mediated by an enzyme distinct from amylo-l,6-glucosidase. The instability of weak solutions of crystalline [beta]-amylase was investigated and overcome by the addition of glutathione and serum albumin.