ADP-Glucose Pyrophosphorylase, a Regulatory Enzyme for Bacterial Glycogen Synthesis

Abstract

The accumulation of α-1,4-polyglucans is an important strategy to cope with transient starvation conditions in the environment. In bacteria and plants, the synthesis of glycogen and starch occurs by utilizing ADP-glucose as the glucosyl donor for elongation of the α-1,4-glucosidic chain. The main regulatory step takes place at the level of ADP-glucose synthesis, a reaction catalyzed by ADP-Glc pyrophosphorylase (PPase). Most of the ADP-Glc PPases are allosterically regulated by intermediates of the major carbon assimilatory pathway in the organism. Based on specificity for activator and inhibitor, classification of ADP-Glc PPases has been expanded into nine distinctive classes. According to predictions of the secondary structure of the ADP-Glc PPases, they seem to have a folding pattern common to other sugar nucleotide pyrophosphorylases. All the ADP-Glc PPases as well as other sugar nucleotide pyrophosphorylases appear to have evolved from a common ancestor, and later, ADP-Glc PPases developed specific regulatory properties, probably by addition of extra domains. Studies of different domains by construction of chimeric ADP-Glc PPases support this hypothesis. In addition to previous chemical modification experiments, the latest random and site-directed mutagenesis experiments with conserved amino acids revealed residues important for catalysis and regulation

The evolution of contact-dependent inhibition in non-growing populations ofEscherichia coli

“…A biochemical clue to the reason for the high glycogen phenotype of these mutants is provided by the finding that the G336D glgC mutation increases enzymatic activity and alters the allosteric behaviour of ADP-glucose pyrophosphorylase (Ballicora et al 2003). This overproduction of glycogen appears to be necessary for the inhibition of ancestral cells.…”

“…We found that in this evolved ABM, SCDI can be attributed to single base substitution mutations in glgC, which encodes ADP-glucose pyrophosphorylase, a regulatory enzyme that catalyses the first reaction of bacterial glycogen synthesis (Ballicora et al 2003). The details of the procedures used to identify this gene and demonstrate that it is responsible for both the immunity of the evolved strains to killing and their ability to kill the ancestral strain are presented in the electronic supplementary material.…”

Modulation of Allosteric Regulation by E38K and G101N Mutations in the Potato Tuber ADP-glucose Pyrophosphorylase

“…27) Although the expression of these mutant enzymes in transgenic Arabidopsis exhibited higher starch content than plants expressing ALS-WT at the end of light 10.0 (39) 5.4 (21) 1.9 (7) 3.5 (11) 3.5 (13) All enzyme activities were determined from ADP-glucose synthesis assay data of three independent experiments, and the SE were within 15% in all cases. Specific activities (U/mg) of the enzymes are presented.…”

“…[9][10][11][12][13] The specific phosphate ester molecule is evolutionarily adapted to controlling carbon flux in the major carbon metabolic pathway. The results obtained here show the possibility of extending the specificity of the allosteric effectors of plant AGPase activity, and in turn of increasing the net catalytic activity of AGPase for enhanced starch production.…”

“…Bacterial AGPases are activated by pyruvate (PYR), fructose 6-phosphate (F6P), and fructose 1,6-bisphosphate (F16BP), and are inhibited by AMP. 9,10) On the other hand, the activator and the inhibitor of higher plant AGPases are 3-phosphoglycerate (3-PGA) and orthophosphate (Pi) respectively. [11][12][13] In contrast to bacterial AGPase, a homotetrameric protein, the higher plant AGPase is composed of two small subunits (SSs) and two large subunits (LSs), which form a heterotetramer.…”