ADP-glucose pyrophosphorylase, a regulatory enzyme for bacterial glycogen synthesis.
The accumulation of alpha-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 alpha-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.
Ballicora
Miguel A
MA
Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, USA.
Iglesias
Alberto A
AA
Preiss
Jack
J
D000595:Amino Acid Sequence; D001419:Bacteria / Q000201:enzymology / Q000378:metabolism*; D005936:Glucans / Q000096:biosynthesis; D051599:Glucose-1-Phosphate Adenylyltransferase; D006003:Glycogen / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D009713:Nucleotidyltransferases / Q000378:metabolism*; D010944:Plants / Q000201:enzymology / Q000378:metabolism; D011487:Protein Conformation; D016415:Sequence Alignment
D005936:Glucans; D006003:Glycogen; D009713:Nucleotidyltransferases; D051599:Glucose-1-Phosphate Adenylyltransferase