Abstract
Fructose-1,6-bisphosphate activates ADP-glucose pyrophosphorylase and the synthesis of glycogen in Escherichia coli. Here, we show that although pyruvate is a weak activator by itself, it synergically enhances the fructose-1,6-bisphosphate activation. They increase the enzyme affinity for each other, and the combination increases V max, substrate apparent affinity, and decreases AMP inhibition. Our results indicate that there are two distinct interacting allosteric sites for activation. Hence, pyruvate modulates E. coli glycogen metabolism by orchestrating a functional network of allosteric regulators. We postulate that this novel dual activator mechanism increases the evolvability of ADP-glucose pyrophosphorylase and its related metabolic control.
Highlights
Both glycogen synthesis in bacteria and starch synthesis in plants share a key metabolic step: synthesis of the glucosyl-donor ADP-glucose (ADP-Glc)
In this work we found an important role for Pyr in the E. coli ADP-Glc PPase
ADP-Glc PPases from diverse sources are classified according to their allosteric effectors [1,2]
Summary
Both glycogen synthesis in bacteria and starch synthesis in plants share a key metabolic step: synthesis of the glucosyl-donor ADP-glucose (ADP-Glc). The reaction is catalyzed by ADP-Glc pyrophosphorylase (EC: 2.7.7.27; ADP-Glc PPase), which is allosterically regulated by metabolites from the main carbon assimilation route in the respective organism [1,2]. It belongs to an enzyme family with kinetic properties adapted to different metabolic environments. This is evidenced by a certain degree of promiscuity observed for the substrate and/or activator in some of the groups [3,4]. In this work we found an important role for Pyr in the E. coli ADP-Glc PPase
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