Yeast Polyphosphatases PPX1 and PPN1: Properties, Functions, and Localization
The PPX1 and PPN1 genes of Saccharomyces cerevisiae encode the enzymes that hydrolyze inorganic polyphosphates (polyP) of different chain lengths including tripolyphosphate. They are divalent metal ion dependent. PPX1 is an exopolyphosphatase splitting Pi
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Yeast Polyphosphatases PPX1 and PPN1: Properties, Functions, and Localization Nadeshda Andreeva, Lidia Lichko, Ludmila Trilisenko, Ivan V. Kulakovskiy, and Tatiana Kulakovskaya
Abstract
The PPX1 and PPN1 genes of Saccharomyces cerevisiae encode the enzymes that hydrolyze inorganic polyphosphates (polyP) of different chain lengths including tripolyphosphate. They are divalent metal ion dependent. PPX1 is an exopolyphosphatase splitting Pi from polyP chain end. PPN1 displays exopolyphosphatase and endopolyphosphatase activities in the presence of cobalt and magnesium ions, respectively. PPN1 prefers long-chain polyP, while PPX1 prefers short-chain polyP. Commonly, PPX1 is localized in the cytoplasm and mitochondrial matrix, while PPN1 is localized in the vacuoles, nuclei, and mitochondrial membrane. PPN1 appears in the cytoplasm at the early growth stage under phosphate excess. The PPX1 or PPN1 knockouts increase polyP content in S. cerevisiae. ΔPPN1 mutants contain polyP with longer chains, while ΔPPX1 does not demonstrate polyP chain elongation. PPX1 overexpression has no effect on polyP content and chain length. In turn, PPN1 overexpression decreases polyP content. Both PPX1 and PPN1 catalyze the same reaction, but there is no similarity between the amino acid sequences of these enzymes.
N. Andreeva • L. Lichko • L. Trilisenko Skryabin Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russia I.V. Kulakovskiy Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilova 32, Moscow 119991, Russia Vavilov Institute of General Genetics, Russian Academy of Sciences, Gubkina, 3, Moscow 119991, Russia T. Kulakovskaya (*) Laboratory of Regulation of Biochemical Processes, Skryabin Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russia e-mail: [email protected] © Springer International Publishing Switzerland 2016 T. Kulakovskaya et al. (eds.), Inorganic Polyphosphates in Eukaryotic Cells, DOI 10.1007/978-3-319-41073-9_2
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Furthermore, the human ortholog of PPX1, the prune protein, has an exopolyphosphatase activity, but neither functional nor structural homologs of PPN1 have been found in higher eukaryotes.
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Introduction
Inorganic polyphosphate (polyP, polyPn, where n is the average number of phosphate residues in the polymer chain) is a linear polymer containing a few to several hundred orthophosphate residues linked by energy-rich phosphoanhydride bonds. This polymer is an essential component of yeast cells containing polyP in all cellular compartments (Kulaev et al. 2004). Many enzymes are involved in polyP metabolism in the yeast Saccharomyces cerevisiae. Exopolyphosphatase (polyphosphate phosphohydrolase EC 3.6.1.11) cleaves Pi from the end of the polyP chain: PolyPn + H2O → PolyPn−1 + Pi Endopolyphosphatase (polyphosphate depolymerase, EC 3.6.1.10.) splits long polyP molecules into shorter ones: PolyPn + H2O → Oli
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