Role of glucose-1-phosphate and glucose-6-phosphate in glycogen synthesis by pigeon liver homogenate☆

Abstract 1. 1. Glucose-1-C 14 , G-6-P-1-C 14 and G-1-P-l-C 14 have been incubated with a pigeon liver homogenate. Incorporation of C 14 into glycogen and CO 2 were measured. 2. 2. The relative incorporation of C 14 from G-6-P-1-C 14 and glucose-1-C 14 into glycogen and CO 2 together with the relative incorporation of C 14 from G-1-P-l-C 14 and glucose-1-C 14 into glycogen and CO 2 were calculated. From these results, it is postulated that G-6-P is not a necessary intermediate in glycogen biosynthesis from glucose; G-1-P would be the first intermediate and the metabolic cross that leads to glycogen and CO 2 . 3. 3. It is suggested that G-1-P is formed directly from glucose through the reactions catalyzed by phosphoglucokinase (E.C. 2.7.1.10) and phosphodismutase (E.C. 2.7.1.41). 4. 4. This last hypothesis is supported by the fact that G-1-P and G-1,6-diP stimulated C 14 incorporation from glucose-1-C 14 into both CO 2 and glycogen. Other minor facts obtained from this work and others from the literature help to sustain the postulations here discussed.