An Update on Polyphosphate In Vivo Activities

Abstract

Polyphosphate (polyP) is an evolutionary ancient inorganic molecule widespread in biology, exerting a broad range of biological activities. The intracellular polymer serves as an energy storage pool and phosphate/calcium ion reservoir with implications for basal cellular functions. Metabolisms of the polymer are well understood in procaryotes and unicellular eukaryotic cells. However, functions, regulation, and association with disease states of the polymer in higher eukaryotic species such as mammalians are just beginning to emerge. The review summarises our current understanding of polyP metabolism, the polymer's functions, and methods for polyP analysis. In-depth knowledge of the pathways that control polyP turnover will open future perspectives for selective targeting of the polymer.

Keywords: contact activation; energy metabolism; exopolyphosphatase; polyphosphate.

Figure 1

Gross structures of natural polyP. (A): PolyP is a polymer consisting of 3–1000 tetrahedral phosphate subunits linked to each other via a shared oxygen atom. Most polyP is linear; however, branched forms exist. (B): PolyP binds Ca²⁺, which binds further polyP and lines up, presumably in a helical secondary structure [27]. (C): Aggregated Ca²⁺ polyP forms nanoparticles that, in turn, form microsomes within cells.