Glycogen debranching enzyme: Difference between revisions

Revision as of 01:25, 17 April 2020

Revision as of 23:33, 26 September 2020

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== Function ==

Together with [[phosphorylase]], glycogen debranching enzymes function in [[glycogenolysis|glycogen breakdown]] and glucose mobilization. When phosphorylase has digested a glycogen branch down to four glucose residues, it will not remove further residues. Glycogen debranching enzymes assist phosphorylase, the primary enzyme involved in [[Glycogenolysis|glycogen breakdown]], mobilizein the mobilization of glycogen stores. Phosphorylase can only cleave α-1,4- glycosidic bond between adjacent glucose molecules in glycogen but branches also exist as α-1,6 linkages. When phosphorylase reaches four residues from a branching point it stops cleaving; because 1 in 10 residues is branched, cleavage by phosphorylase alone would not be sufficient in mobilizing glycogen stores.<ref name=Berg/><ref name=Hondoh/> Before phosphorylase can resume catabolism, debranching enzymes perform two functions:

* 4-α-D-glucanotransferase ({{EC number|2.4.1.25}}), or [[glucosyltransferase]], transfers three glucose [[residue (chemistry)|residues]] from the four-residue glycogen branch to a nearby branch. This exposes a single glucose residue joined to the glucose chain through an α -1,6 glycosidic linkage<ref name="Berg"/>