The diversity of glycogen branching enzymes in microbes

Glycogen is the major carbon and energy reserve polymer in microorganisms and animals. Glycogen branching enzyme is one of the key enzymes in the glycogen synthesis. The glycogen branching enzymes were classified into GH13 and GH57 families. In this thesis, the two families GBEs were compared from crystal structures to their branched products. The GH13 GBEs are more active on starches than GH57 GBEs, while GH57 GBEs with high relative hydrolytic activity produce the products with more oligosaccharide. The two families GBEs in on bacteria shows that GH13 GBE is involved in glycogen synthesis, and the real function of GH57 GBE is not clear yet. The molecular weight of branched α-glucans increases with increasing amylose of the substrate for both families GBEs. The two families GBEs can be used to produce resistant starches with high amount of α-1,6-binds