The Molecular Structure of Glycogens

Abstract

This chapter discusses the molecular structure of glycogens. Glycogens, from vertebrate, invertebrate, bacterial, and yeast cells, are multiply-branched molecules (molecular weight ∼10 7 ) consisting of chains of α-(1 → 4)-linked D-glucose residues. The chains that are arranged in a tree- or bush-like form, normally contain an average of about 12 D-glucose residues; 40-50% of these may be removed by β-amylase. The exterior portions of the chains are therefore longer than those in the interior of the molecules, where adjacent branch points are separated by only 3–4 D-glucose residues. Small variations in molecular structure are shown by glycogens from different biological sources. A small proportion of glycogens may be expected to have abnormal structures. In this connection, the isolation of maltulose (some 5 %) from α-amylolytic digest of glycogen of pregnant-rabbit liver would suggest that D-fructose may be an extremely rare but minor component of certain glycogens.