1,4-Alpha-Glucan Branching Enzyme 1 (GBE1)

GBE1 is a glycogen branching enzyme that catalyzes the transfer of alpha-1,4-linked glucosyl units from the outer end of a glycogen chain to an alpha-1,6 position on the same or a neighboring glycogen chain. Branching of the chains is essential to increase the solubility of the glycogen molecule and, consequently, in reducing the osmotic pressure within cells. Highest level of this enzyme are found in liver and muscle. The human and yeast glycogen branching enzymes were found to have 67% identical amino acid sequence over a major portion of their length. The full length of the cDNA was approximately 3 kb. The coding sequence contained 2,106 bp encoding a 702-amino acid protein. The calculated molecular mass of the GBE1 protein, derived from its cDNA sequence, was 80,438 Da.