A study of the reaction catalysed by the liver branching enzyme

Abstract

The mechanism of action of liver branching enzyme has been studied by using as substrate 2 polysaccharides in which the non-reducing ends had been labeled by incubation with phosphorylase and a trace amount of [C14]glucose-l-phosphate. After these polysaccharides had been treated with branching enzyme, their structure was analyzed by period-ate oxidation, by degradation with phosphorylase any amylo-(1[forward arrow]6)-glucosidase and by degradation with pullulanase. All the results indicate that the branching enzyme catalyzes the transfer from (1[forward arrow]4)- to (1[forward arrow]6)-linkage of a chain of glucose units, the minimum length of which is 6 glucose units. A maltodextrin containing 16 glucose units was not acted on by the branching enzyme.