In order to use phosphorus as the building block for macromolecules and nucleotides, cells take up inorganic phosphate (Pi) from the environment. During phosphate storage, Pi can be polymerised into polyphosphate (polyP), which is stored in membrane-enclosed compartments called acidocalcisomes in prokaryotic and eukaryotic microorganisms. PolyP is used in numerous cellular processes, such as heavy metal detoxification, the stress response, and blood clotting and inflammation, in mammalian cells. However, the knowledge of the enzymes responsible for the regulation and turnover of polyP still remains very limited. In this issue (p. 1625), Rūta Gerasimaitė and Andreas Mayer identify a new polyphosphatase in Saccharomyces cerevisiae, which is sorted to acidocalcisome-like vacuoles through the multivesicular body pathway. The enzyme is named Ppn2, as it shows a major polyphosphatase activity to mobilise polyP – together with the vacuolar polyphosphatase Ppn1 – in response to phosphate starvation. The authors also show that Ppn2 requires Zn2+ ions and is part of the phosphoprotein phosphatase superfamily. The identification of a second polyphosphatase in the vacuole is an important new finding that will help experimenters dissect the regulation of polyP metabolism and its impact on phosphate and energy homeostasis of the cell.
A new polyphosphatase in yeast
A new polyphosphatase in yeast. J Cell Sci 1 May 2017; 130 (9): e0905. doi:
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