ONE of the major advances of medical science was the demonstration of in vitro synthesis of glycogen by purified phosphorylase. This discovery was the forerunner of an explosive increase in knowledge of the processes of biosynthesis. The rapid unfolding of the nature of enzymatic reactions has revolutionized biochemistry and is beginning to have a major impact on all aspects of biology and medicine.
Concepts of the enzymatic reactions responsible for the biosynthesis of polysaccharides have been completely changed in the past 10 years as a result of the discovery of uridine nucleotides. According to recent reports,1 uridine diphosphate glucose is the key intermediate in the synthesis of glycogen. This nucleotide, originally discovered by Leloir2 as the coenzyme involved in the interconversion of glucose and galactose, is composed of uracil, ribose, two phosphate groups, and glucose. The uridine portion of the molecule (uracil, ribose, and phosphate) is a component