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Alsberg-French-Schoch Award - Role of carbohydrate-active enzymes in glycogen and starch metabolism.
K. H. PARK (1). (1) Seoul National University, Center for Food and Bioconvergence and Department of Food Science and Biotechnology, Seoul, , Korea
Many bacteria, plants, green algae, and cyanobacteria synthesize glycogen or starch using a similar ADP glucose-based pathway. However, plant starch metabolism can be distinguished from bacterial glycogen metabolism by the multiple forms of enzymes involved in each step of the pathway. In the study described herein, the roles of debranching enzyme (GlgX) and amylomaltase (MalQ) were investigated in Escherichia coli. Our results suggest a common pathway of plant starch metabolism. First, maltodextrinyl-1,6 β cyclodextrin, a glycogen mimic substrate, was synthesized to study structurally complicated macromolecules, such as glycogen or starch, and subsequently used to analyze the enzymatic reaction. Structural determination of GlgX revealed a molecular explanation of its unique substrate specificity toward short branch chains, which likely shares substrate specificity for short branch chains with isoamylase 3 in plants. Characterization of MalQ (analogous to disproportionating enzyme 2 (DPE2) in plants) suggests that MalQ is involved alongside GlgX in glycogen catabolism. Finally, we discuss bacterial glycogen enzymes and important implications for understanding the starch degradation pathway.
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