In vitro formation and growth of glycogen: experimental verification of theoretical predictions

Glycogen is a complex branched glucose polymer that serves as energy reservoir in animals and some bacteria; it has also been synthesized in vitro. It comprises small β particles linked in large aggregates termed α particles. Theory, based on the evolutionary processes which cause these particles to be formed, suggests that if all ingredients for in vitro particle synthesis were added to a suspension of α particles, then these will grow to a steady-state size distribution, after which new particles will be formed. Here, this prediction is experimentally tested and found to be verified, using in vitro glycogen β particles as the starting point. The latter were made by the method of Ciric and Loos, Carbohydrate Polymers 2013, 93, 31; this was chosen because there are considerably less components than in an in vivo system, namely glycogen synthase, glycogen branching enzyme, glycogen debranching enzyme, glycogen phosphorylase and α-glucosidase. It was also found that new-particle formation was only found starting with β particles formed in vivo, but not with those synthesized in vitro; this implies that in vivo β particles contain one or more substances additional to those in the "minimal" in vitro particle synthesis used here. HYPOTHESIS: In glycogen, β particles already contain some buds on their surface, so they might have the potential to form α particles.