An exopolyphosphatase of Escherichia coli. The enzyme and its ppx gene in a polyphosphate operon.
A gene, ppx, that encodes a novel exopolyphosphatase of 513 amino acids (58,133 Da) was found downstream of the gene for polyphosphate kinase, ppk. Transcription of the ppx gene depends on the ppk promoters, indicating a polyphosphate (polyP) operon of ppk and ppx. Exopolyphosphatase, purified to homogeneity from overproducing cells, is judged to be a dimer of 58-kDa subunits. Orthophosphate is released processively from the ends of polyP approximately 500 residues long, but chains of approximately 15 residues compete poorly with polyP as substrate; ATP is not a substrate. Mg2+ (1 mM) and a high concentration of K+ (175 mM) support optimal activity.
Department of Biochemistry, Stanford University School of Medicine, California 94305-5307.
M
M
Akiyama
E
E
Crooke
A
A
Kornberg
D017766:Acid Anhydride Hydrolases; D000595:Amino Acid Sequence; D001483:Base Sequence; D002852:Chromatography, Ion Exchange; D004269:DNA, Bacterial / Q000235:genetics / Q000302:isolation & purification; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics*; D005798:Genes, Bacterial; D007700:Kinetics; D046911:Macromolecular Substances; D015636:Magnesium Chloride / Q000494:pharmacology; D008969:Molecular Sequence Data; D009876:Operon; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D010957:Plasmids; D011122:Polyphosphates / Q000378:metabolism; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D015183:Restriction Mapping; D013379:Substrate Specificity; D013816:Thermodynamics
D004269:DNA, Bacterial; D046911:Macromolecular Substances; D011122:Polyphosphates; D011994:Recombinant Proteins; D015636:Magnesium Chloride; D010744:Phosphoric Monoester Hydrolases; D017766:Acid Anhydride Hydrolases; C020137:exopolyphosphatase