Disease relevance of ppx

• An exopolyphosphatase of Escherichia coli. The enzyme and its ppx gene in a polyphosphate operon [1].
• Cloning and characterization of polyphosphate kinase and exopolyphosphatase genes from Pseudomonas aeruginosa 8830 [2].
• Subpicomole amounts of polyP (0.5 pmol/100 micrograms of protein) were determined by its conversion to ATP by Escherichia coli polyphosphate kinase and, alternatively, to Pi by Saccharomyces cerevisiae exopolyphosphatase [3].

High impact information on ppx

• Inasmuch as the activities of the principal enzymes that synthesize and degrade polyP fluctuate only slightly, the polyP accumulation can be attributed to a singular and profound inhibition by pppGpp and/or ppGpp of the hydrolytic breakdown of polyP by exopolyphosphatase, thereby blocking the dynamic turnover of polyP [4].
• The exopolyphosphatase is an ASKHA (acetate and sugar kinases, Hsp70, actin) phosphotransferase with an active site found in a cleft between the two amino-terminal domains [5].
• On-column refolding of an insoluble histidine tag recombinant exopolyphosphatase from Trypanosoma brucei overexpressed in Escherichia coli [6].
• To elucidate the functions of poly(P) in the regulation of gene expression, the level of cellular poly(P) in Escherichia coli was reduced to a barely detectable concentration by overproduction of exopolyphosphatase (exopoly(P)ase) with a plasmid encoding yeast exopoly(P)ase (Shiba et al., Proc. Natl. Acad. Sci. USA 94 (1997) 11210-11215) [7].

Biological context of ppx

• However, no coregulation between ppk and ppx promoters has been demonstrated in response to osmotic shock or oxidative stress [2].

Associations of ppx with chemical compounds

• In contrast, the mutant strain carrying multiple copies of ppk and ppx produced 1/20 of the polyphosphate found in the strain carrying multiple copies of ppk only and showed no significant increase in doubling time over the same cadmium concentration range [8].

Other interactions of ppx

• Expression of the exopolyphosphatase gene (ppx) immediately downstream of ppk in the operon was likewise disrupted [9].

Analytical, diagnostic and therapeutic context of ppx

• An exopolyphosphatase gene has been cloned by polymerase chain reaction (PCR) from Trypanosoma brucei and the corresponding protein overexpressed as a recombinant His-tag (histidine tag) exopolyphosphatase in E. coli in order to characterize its biochemical activity and to produce antibody to determine its localization [6].

References