Polyphosphate: popping up from oblivion

Abstract

Phosphate is one of the essential elements supporting life. Cells accumulate phosphate in the form of a molecule called polyphosphate (polyP), which carries many functions in the physiology of cells that have not been wholly elucidated. Polyphosphate is present in all the types of cells from bacteria to mammals. It consists of a linear polymer constructed with anywhere from a few to hundreds of inorganic phosphate (Pi) molecules linked by phosphoanhydride bonds. Although polyP was described many years ago, difficulties in the study of its roles, most likely due to the many processes polyP is involved in and incomplete information obtained from multiple models and organisms relegate polyP into oblivion. But now, several interesting pieces of evidence are resurrecting the polyP as a key molecule in processes, such as protein folding, carbon metabolism, cell cycle progression, dNTP synthesis, and genomic stability. In this contribution, in addition to briefly summarize the polyP history and roles, we discuss its involvement in supporting cell cycle progression and genomic stability as well as the implications for the truthful replication of genomes.

Molecular Mechanisms of Phosphate Homeostasis in <i>Escherichia coli</i>

“…PolyP is found in all kingdoms of life [81,82]. It is a linear chain of variable length of Pi residues that are linked by phosphoanhydride bonds.…”

Polyphosphatase PPN1 of &lt;i&gt;Saccharomyces cerevisiae&lt;/i&gt; Is a Deoxyadenosine Triphosphate Phosphohydrolase

“…First, PPN1 gene is responsible for the exopolyphosphatase activity in yeast nuclei [27]. Second, ΔPPN1 mutants displayed the impairment of the cell cycle when the cells were grown under Pi limitation [4].…”

“…The enzyme activities were assayed at 30˚ in 0.1 ml of 50 mM Tris-HCl, pH 7.2, containing 0.1 mM CoSO 4 and 200 mM NH 4 Cl. The concentrations of MgSO 4 , MnSO 4 , ZnSO 4 , and other additives are indicated in the legends to the tables and figures. The amount of the enzyme releasing 1 nmole of phosphate (Pi) per 1 min was taken as a unit of enzyme activity (mU).…”

Critical and diverse roles of phosphates in human bone formation

“…16,17 Several distinct biological roles of polyP have been identified in various cell types. 18 Whilst this demonstrates the inter-domain ubiquity of polyP, it makes the exact role of these phosphate species in the origin of cellular life, and within specific cellularly influenced processes such as biomineralisation, difficult to pinpoint.…”

“…These molecules have been implicated in the origin of life as nonenzymatically produced energy carriers and phosphate donors, and several distinct biological roles have been identified since their discovery in cells in the late 19th century. 17,18 PolyP is stored intracellularly in what are commonly referred to as 'dense granules', which are present in both prokaryotes and eukaryotes. In mammals, polyP is particularly concentrated in the granules of platelets; chains around 75 phosphate residues long are present in platelets at a concentration of 1.1 mM, 10-20 fold higher than in major organs.…”