PPN1 encodes a vacuolar fungal endopolyphosphatase-family enzyme that catabolizes inorganic polyphosphate by both internal cleavage and chain-end phosphate release. The protein is made as a single-pass vacuolar membrane precursor, sorted through multivesicular bodies by ubiquitin-dependent internal-vesicle targeting, and proteolytically matured in the vacuole. Ppn1 activity shortens long-chain vacuolar polyphosphate and can also appear in the cytosol under phosphate-rich outgrowth conditions, making it one of the major budding-yeast enzymes that mobilizes stored polyphosphate.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000298 endopolyphosphatase activity | EXP PMID:15792812 Endopolyphosphatase in Saccharomyces cerevisiae undergoes po... | ACCEPT | Summary: Shi and Kornberg purified mature S. cerevisiae Ppn1 to homogeneity, showed that it cleaves long-chain inorganic polyphosphate internally, and mapped the proteolytic processing required to activate the 674-aa precursor. Reason: Endopolyphosphatase activity is the defining biochemical activity of Ppn1; this row is supported by purified enzyme data and by the earlier cloning and mutant evidence showing that YDR452W/PHM5 is the PPN1 structural gene. Supporting Evidence: PMID:15792812 Endopolyphosphatase (Ppn), responsible for cleavage of long chain inorganic polyphosphate (poly P) of several hundred residues to generate progressively shorter chains, has been identified in mammalian cells and purified from Saccharomyces cerevisiae. |
| GO:0000298 endopolyphosphatase activity | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT assigns endopolyphosphatase activity at the fungal PPN1 node PTN000818947, seeded by the S. cerevisiae PPN1 experimental record; Q04119 is the seed and the PTHR10340:SF55 reference member. Reason: The IBD node is correctly placed on the fungal Ppn1 clade, which separates PPN1 enzymes from the metazoan acid sphingomyelinase/SMPDL3 branches in the same metallo-dependent phosphatase superfamily. The SGD seed is PPN1 itself, which is direct experimental evidence for placing the inherited fungal activity, not a circular donor. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN000818947 SUPPORTS TRANSFER PTN000818947 is the fungal PPN1 node with an IBD for endopolyphosphatase activity and IRDs that stop animal acid-sphingomyelinase terms from entering the fungal clade. Supporting Evidence: file:interpro/panther/PTHR10340/PTHR10340-paint.tsv PTHR10340 PTN000818947 GO:0000298 F IBD false SGD:S000002860 taxon:4751 20180112 PMID:11447286 That PPN1 encodes Ppn1 was verified by a 25-fold increase in Ppn1 when overexpressed under a GAL promoter and also by several peptide sequences that match exactly with sequences in a yeast genome ORF, the mutation of which abolishes Ppn1 activity. |
| GO:0000298 endopolyphosphatase activity | IDA PMID:11447286 The endopolyphosphatase gene: essential in Saccharomyces cer... | ACCEPT | Summary: Sethuraman, Rao and Kornberg purified Ppn1, matched its peptides to YDR452W/PHM5, overexpressed PPN1 to increase activity 25-fold, and deleted PPN1 to abolish Ppn1 activity. Reason: The purified-enzyme, peptide-mapping, overexpression and null-mutant experiments identify Q04119 as the endopolyphosphatase that internally shortens long-chain polyphosphate. Supporting Evidence: PMID:11447286 The Ppn1 gene (PPN1) now has been cloned, sequenced, overexpressed, and deleted. PMID:11447286 That PPN1 encodes Ppn1 was verified by a 25-fold increase in Ppn1 when overexpressed under a GAL promoter and also by several peptide sequences that match exactly with sequences in a yeast genome ORF, the mutation of which abolishes Ppn1 activity. |
| GO:0000298 endopolyphosphatase activity | IDA PMID:31175919 Ppn2 endopolyphosphatase overexpressed in Saccharomyces cere... | ACCEPT | Summary: Andreeva and colleagues purified Ppn1 from overexpressing yeast and directly compared it with Ppn2, Ppx1 and Ddp1, confirming Ppn1 endopolyphosphatase activity. Reason: The 2019 purified-enzyme comparison independently supports Ppn1's internal polyphosphate cleavage and distinguishes it from the PPX1 exopolyphosphatase. Supporting Evidence: PMID:31175919 Ppn2, Ppn1, and Ddp1 had endopolyphosphatase activities, whereas Ppx1 did not. |
| GO:0000298 endopolyphosphatase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Combined automated annotation from the PPN1/endopolyphosphatase family, RHEA:22452, and EC 3.6.1.10. The mapping recovers the experimentally established Ppn1 endopolyphosphatase reaction. Reason: UniProt now carries the same endopolyphosphatase catalytic activity with direct evidence from Shi and Kornberg and Andreeva et al.; the electronic assertion is exact rather than merely hydrolase-level. Supporting Evidence: file:genes/yeast/PPN1/PPN1-uniprot.txt Reaction=[phosphate](n+1) + n H2O = (n+1) phosphate + n H(+); Xref=Rhea:RHEA:22452 |
| GO:0000298 endopolyphosphatase activity | IMP PMID:11447286 The endopolyphosphatase gene: essential in Saccharomyces cer... | ACCEPT | Summary: PPN1 disruption abolished Ppn1 activity and altered long-chain polyphosphate accumulation in vivo. Reason: The mutant phenotype is paired with the cloned, overexpressed structural gene in the same study and supports the direct enzymatic assignment. Supporting Evidence: PMID:11447286 Further studies of disruption and overexpression of the gene (see below) confirmed that YDR452w is the structural gene for Ppn1. PMID:11447286 The Ppn1-deficient strains were also lacking in Ppn1 activity |
| GO:0000324 fungal-type vacuole | HDA PMID:26928762 One library to make them all: streamlining the creation of y... | ACCEPT | Summary: High-throughput SWAT tagging placed Ppn1 in the vacuolar system, consistent with directed localization and biochemical evidence that Phm5/Ppn1 is a vacuolar polyphosphatase. Reason: The genome-scale paper establishes the tagged yeast endomembrane library used for the HDA call; the same fungal-type vacuole localization is independently supported by the Phm5-GFP MVB/vacuole study and by UniProt's curated vacuolar membrane record. Supporting Evidence: PMID:26928762 we constructed and investigated a library of βΌ1,800 strains carrying SWAT-GFP modules at the amino termini of endomembrane proteins PMID:11566881 We tagged Phm5p, Hmx1p, Sna3p and Cps1p with GFP and expressed them in a wild-type strain |
| GO:0000324 fungal-type vacuole | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT assigns fungal-type vacuole at the fungal PPN1 node PTN000818947, seeded by S. cerevisiae PPN1. Reason: Vacuolar localization is inherited by the fungal Ppn1 clade and is the correct fungal-specific cellular-component term for the vacuolar endopolyphosphatase branch of PTHR10340. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN000818947 SUPPORTS TRANSFER PTN000818947 supports fungal vacuole localization for Q04119 and the other fungal Ppn1 members. Supporting Evidence: file:interpro/panther/PTHR10340/PTHR10340-paint.tsv PTHR10340 PTN000818947 GO:0000324 C IBD false SGD:S000002860 taxon:4751 20180112 file:genes/yeast/PPN1/PPN1-uniprot.txt SUBCELLULAR LOCATION: Vacuole membrane |
| GO:0000329 fungal-type vacuole membrane | IDA PMID:11566881 Sorting of proteins into multivesicular bodies: ubiquitin-de... | KEEP AS NON CORE | Summary: Reggiori and Pelham identified Phm5/Ppn1 in internal vesicles of multivesicular bodies and showed that GFP-Phm5 is sorted into the vacuole lumen. Reason: Ppn1 is a single-pass membrane precursor sorted through the fungal-type vacuole membrane, and some signal is seen at the limiting vacuolar membrane when internal-vesicle sorting is perturbed. The mature catalytic enzyme is mainly activated after vacuolar delivery, so the membrane row is retained as a trafficking/localization detail rather than as the core active site. Supporting Evidence: PMID:11566881 We detected three new proteins that follow the same pathway as Cps1p: a polyphosphatase (Phm5p), a protein with homology to haem oxygenases (Hmx1p) and a possible proton transporter (Sna3p). PMID:11566881 These results confirm that Cps1p, Phm5p, Hmx1p and Sna3p all normally reach the vacuole from late endosomes |
| GO:0000329 fungal-type vacuole membrane | IMP PMID:11566881 Sorting of proteins into multivesicular bodies: ubiquitin-de... | KEEP AS NON CORE | Summary: Mutation of the Phm5 cytosolic tail and ubiquitin availability altered Phm5 sorting between the vacuolar lumen/internal vesicles and the vacuolar membrane. Reason: The mutant trafficking experiments show that Phm5/Ppn1 is a vacuolar membrane cargo whose ubiquitination controls sorting into intralumenal MVB vesicles. That is sound localization evidence, but it is not the catalytic core of the enzyme. Supporting Evidence: PMID:11566881 Mutation of Lys6 to either glycine (not shown) or arginine caused the protein to accumulate on the vacuole membrane, just as it did in the Ξdoa4 strain (Figure 8 ). PMID:11566881 the addition of ubiquitin was sufficient to restore delivery of the Phm5p K6R mutant to the vacuole interior, in all cells |
| GO:0004309 exopolyphosphatase activity | EXP PMID:15170373 Purification and properties of exopolyphosphatase from the c... | ACCEPT | Summary: The 2004 study purified a PPX1-independent cytosolic high-molecular-mass exopolyphosphatase; a subsequent 2006 study assigned this activity to PPN1. Reason: The original purification found the activity before the encoding gene was assigned, but the later peptide and gene evidence identified the same high-molecular-mass cytosolic exopolyphosphatase as a PPN1 product. Supporting Evidence: PMID:15170373 A novel exopolyphosphatase has been isolated from the cytosol of Saccharomyces cerevisiae PMID:17009950 It has been shown that the high molecular mass exopolyphosphatase localized in cytosol of the yeast Saccharomyces cerevisiae is encoded by the PPN1 gene. |
| GO:0004309 exopolyphosphatase activity | EXP PMID:31175919 Ppn2 endopolyphosphatase overexpressed in Saccharomyces cere... | ACCEPT | Summary: Ppn1 purified from an overexpressing strain has strong exopolyphosphatase activity in the same assay set that confirmed its endopolyphosphatase activity. Reason: Ppn1 releases terminal phosphate from polyphosphate and remains a strong exopolyphosphatase relative to Ppn2 and Ddp1 in purified-enzyme comparisons. Supporting Evidence: PMID:31175919 Ppx1 and Ppn1 exhibited high and Ddp1 and Ppn2 low exopolyphosphatase activity: 240, 500, 0.05 and 0.1 U/mg protein, respectively. |
| GO:0004309 exopolyphosphatase activity | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT assigns exopolyphosphatase activity to the fungal PPN1 clade PTN000818947, seeded by the S. cerevisiae PPN1 record. Reason: Exopolyphosphatase activity is conserved in fungal Ppn1 proteins, and the IBD is placed on the same fungal node as the endopolyphosphatase and vacuolar polyphosphate catabolism assertions. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN000818947 SUPPORTS TRANSFER PTN000818947 carries the fungal Ppn1 exopolyphosphatase IBD and is the correct source for this inherited activity. Supporting Evidence: file:interpro/panther/PTHR10340/PTHR10340-paint.tsv PTHR10340 PTN000818947 GO:0004309 F IBD false SGD:S000002860 taxon:4751 20180112 PMID:17009950 It has been shown that the high molecular mass exopolyphosphatase localized in cytosol of the yeast Saccharomyces cerevisiae is encoded by the PPN1 gene. |
| GO:0004309 exopolyphosphatase activity | IDA PMID:17009950 High molecular mass exopolyphosphatase from the cytosol of t... | ACCEPT | Summary: The high-molecular-mass exopolyphosphatase in cytosol is encoded by PPN1 and releases orthophosphate from the beginning of polyphosphate hydrolysis. Reason: This directly assigns the PPX1-independent exopolyphosphatase to PPN1 and completes the gene assignment of the earlier cytosolic exopolyphosphatase purification. Supporting Evidence: PMID:17009950 This enzyme is expressed under special culture conditions when stationary phase cells are passing on to new budding on glucose addition and phosphate excess. PMID:17009950 The enzyme under study releases orthophosphate from the very beginning of polyphosphate hydrolysis. |
| GO:0004309 exopolyphosphatase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Combined automated annotation from the UniProt RHEA:21528/EC:3.6.1.11 catalytic-activity assertion. This is the correct Ppn1 exopolyphosphatase reaction. Reason: The electronic EC/RHEA mapping is grounded in direct PPN1 experiments and matches the supported chain-end phosphate-release activity. Supporting Evidence: file:genes/yeast/PPN1/PPN1-uniprot.txt Reaction=[phosphate](n) + H2O = [phosphate](n-1) + phosphate + H(+); Xref=Rhea:RHEA:21528 |
| GO:0004309 exopolyphosphatase activity | IMP PMID:16862600 Inorganic polyphosphate and exopolyphosphatase in the nuclei... | ACCEPT | Summary: The PPN1 mutant eliminates a nuclear exopolyphosphatase activity under the growth conditions assayed. Reason: The abstract-only cached paper shows that inactivation of PPN1 removes the nuclear exopolyphosphatase activity, and independent purified-enzyme work directly confirms that Ppn1 is an exopolyphosphatase. That combination is enough to retain the activity claim, while the separate nucleus localization row remains unresolved. Supporting Evidence: PMID:16862600 Under inactivation of the PPN1 gene encoding another yeast exopolyPase, elimination of the nuclear exopolyPase is observed. PMID:17009950 It has been shown that the high molecular mass exopolyphosphatase localized in cytosol of the yeast Saccharomyces cerevisiae is encoded by the PPN1 gene. |
| GO:0005634 nucleus | IMP PMID:16862600 Inorganic polyphosphate and exopolyphosphatase in the nuclei... | UNDECIDED | Summary: PPN1 inactivation abolishes the nuclear exopolyphosphatase activity described in an abstract-only nuclear polyphosphate study. Reason: The cached record reports loss of nuclear exopolyphosphatase activity in a PPN1 mutant, but it does not show from the abstract that Ppn1 protein itself enters nuclei or exclude indirect loss of activity. Full-text evidence is needed before retaining or removing a nuclear localization for this vacuolar/cytosolic polyphosphatase. Supporting Evidence: PMID:16862600 Under inactivation of the PPN1 gene encoding another yeast exopolyPase, elimination of the nuclear exopolyPase is observed. |
| GO:0005737 cytoplasm | EXP PMID:17009950 High molecular mass exopolyphosphatase from the cytosol of t... | MODIFY | Summary: The source paper specifically localizes the high-molecular-mass PPN1 exopolyphosphatase to cytosol under stationary-to-budding transition conditions. Reason: The annotation is correct but can be made more specific: the paper states cytosol rather than the broader cytoplasm. Proposed replacements: cytosol Supporting Evidence: PMID:17009950 It has been shown that the high molecular mass exopolyphosphatase localized in cytosol of the yeast Saccharomyces cerevisiae is encoded by the PPN1 gene. |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | MODIFY | Summary: UniProt records a PPN1 cytoplasmic form that appears in the cytosol during transition from stationary growth to new budding on glucose and phosphate excess. Reason: Cytoplasmic localization is correct but broad for the source statement; cytosol is the supported GO term. Proposed replacements: cytosol Supporting Evidence: file:genes/yeast/PPN1/PPN1-uniprot.txt The cytoplasmic form appears in the cytosol during the transition of cells from stationary growth phase to new budding on glucose addition and phosphate excess. |
| GO:0005773 vacuole | IEA GO_REF:0000002 | MODIFY | Summary: InterPro2GO recognizes the fungal PPN1 N-terminal domain and maps it to the conserved vacuolar localization of fungal Ppn1 enzymes. Reason: The assertion is correct, but in yeast the exact term should be the fungal-specific GO:0000324 fungal-type vacuole. Proposed replacements: fungal-type vacuole Supporting Evidence: file:genes/yeast/PPN1/PPN1-uniprot.txt SUBCELLULAR LOCATION: Vacuole membrane |
| GO:0005774 vacuolar membrane | EXP PMID:11566881 Sorting of proteins into multivesicular bodies: ubiquitin-de... | MODIFY | Summary: Phm5/Ppn1 is a single-pass membrane protein that is routed from late endosomes into the fungal vacuole interior. Reason: The source supports the fungal vacuolar system, so the generic vacuolar membrane term should be replaced with the yeast-specific fungal-type vacuole membrane term. The membrane association is non-core because Phm5 is a cargo whose mature catalytic enzyme is vacuolar. Proposed replacements: fungal-type vacuole membrane Supporting Evidence: PMID:11566881 The other three proteins are all predicted to be integral membrane proteins. PMID:11566881 Phm5p has a single TMD and is predicted to have a topology similar to that of Cps1p. |
| GO:0005774 vacuolar membrane | EXP PMID:8900207 Endopolyphosphatases for long chain inorganic polyphosphate ... | MODIFY | Summary: The original long-chain endopolyphosphatase preparation was of yeast vacuolar origin. Reason: The cached abstract supports vacuolar localization of the yeast endopolyphosphatase, and the specific fungal-type vacuole membrane term is a better replacement for the generic vacuolar membrane wording supplied by UniProt. Proposed replacements: fungal-type vacuole membrane Supporting Evidence: PMID:8900207 The activity from Saccharomyces cerevisiae, localized in vacuoles, has been purified to homogeneity from a strain that possesses vacuolar proteases. |
| GO:0005774 vacuolar membrane | IEA GO_REF:0000044 | MODIFY | Summary: UniProt records PPN1 as a vacuolar single-pass membrane protein curated from the MVB sorting and vacuolar endopolyphosphatase studies. Reason: The UniProt location is correct but uses the generic vocabulary; the fungal-specific replacement is GO:0000329 fungal-type vacuole membrane. Proposed replacements: fungal-type vacuole membrane Supporting Evidence: file:genes/yeast/PPN1/PPN1-uniprot.txt Single-pass type II membrane protein |
| GO:0005829 cytosol | IDA PMID:17009950 High molecular mass exopolyphosphatase from the cytosol of t... | ACCEPT | Summary: PPN1 encodes a cytosolic high-molecular-mass exopolyphosphatase that appears during phosphate-rich exit from stationary phase. Reason: The cytosolic pool is experimentally supported and active. Although this high-molecular-mass exopolyphosphatase appears under a specific stationary-to-budding growth transition, the PPN1-dependent cytosolic activity is a directly measured arm of Ppn1's polyphosphate-catabolic function. Supporting Evidence: PMID:17009950 This enzyme is expressed under special culture conditions when stationary phase cells are passing on to new budding on glucose addition and phosphate excess. |
| GO:0006797 polyphosphate metabolic process | IDA PMID:11447286 The endopolyphosphatase gene: essential in Saccharomyces cer... | MODIFY | Summary: Ppn1 catabolizes inorganic polyphosphate internally; the process should be the more specific polyphosphate catabolic process rather than the parent metabolic-process term. Reason: Purified Ppn1 degrades long-chain polyphosphate and ppn1 mutants accumulate longer polyphosphate species. That evidence places Ppn1 in polyphosphate catabolism, not synthesis or a generic metabolic role. Proposed replacements: polyphosphate catabolic process Supporting Evidence: PMID:11447286 Ppn1 that cleaves long-chain poly P of 700 residues (P 700 ) internally to create chains of about 60 residues (P 60 ) and 3 residues (P 3 ) was identified in mammalian tissues and purified from yeast ( 15 ). PMID:40291979 Through screening a library of 55 single-gene knockout strains, we identified six mutants (Ξddp1, Ξvip1, Ξppn1, Ξppn2, Ξecm33, and Ξccr4) exhibiting elevated polyP accumulation |
| GO:0006797 polyphosphate metabolic process | IMP PMID:11447286 The endopolyphosphatase gene: essential in Saccharomyces cer... | MODIFY | Summary: PPN1 deletion alters cellular polyphosphate chain length and long-chain polyphosphate accumulation. Reason: The mutant phenotype follows from loss of a polyphosphate-degrading enzyme; GO:0006798 polyphosphate catabolic process captures the role more precisely than the parent term. Proposed replacements: polyphosphate catabolic process Supporting Evidence: PMID:11447286 Null mutants in Ppn1 accumulate long-chain poly P and are defective in growth in minimal media. PMID:40291979 Through screening a library of 55 single-gene knockout strains, we identified six mutants (Ξddp1, Ξvip1, Ξppn1, Ξppn2, Ξecm33, and Ξccr4) exhibiting elevated polyP accumulation |
| GO:0006798 polyphosphate catabolic process | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT assigns fungal PPN1 enzymes to polyphosphate catabolic process at PTN000818947, seeded by S. cerevisiae PPN1 and a Candida albicans PPN1 CGD record. Reason: The node placement is appropriate: Ppn1 enzymes perform the hydrolytic reactions that break polyphosphate down, and both endo- and exopolyphosphatase IBDs are on the same fungal node. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN000818947 SUPPORTS TRANSFER PTN000818947 is the fungal Ppn1 node that executes polyphosphate degradation by endo- and exopolyphosphatase activities. Supporting Evidence: file:interpro/panther/PTHR10340/PTHR10340-paint.tsv PTHR10340 PTN000818947 GO:0006798 P IBD false CGD:CAL0000182615|SGD:S000002860 taxon:4751 20230405 PMID:11447286 Null mutants in Ppn1 accumulate long-chain poly P and are defective in growth in minimal media. |
| GO:0006798 polyphosphate catabolic process | IDA PMID:17009950 High molecular mass exopolyphosphatase from the cytosol of t... | ACCEPT | Summary: PPN1 encodes the high-molecular-mass exopolyphosphatase whose cytosolic activity releases orthophosphate from polyphosphate. Reason: The PPN1-dependent exopolyphosphatase activity directly catabolizes polyphosphate by removing terminal phosphate. Supporting Evidence: PMID:17009950 The enzyme under study releases orthophosphate from the very beginning of polyphosphate hydrolysis. |
| GO:0016020 membrane | IEA GO_REF:0000002 | MODIFY | Summary: InterPro2GO mapped the PPN1/endopolyphosphatase N-terminal family to the broad membrane term. Reason: Ppn1 is a single-pass fungal vacuolar membrane precursor. The broad membrane call should be replaced by fungal-type vacuole membrane. Proposed replacements: fungal-type vacuole membrane Supporting Evidence: PMID:11566881 Phm5p has a single TMD and is predicted to have a topology similar to that of Cps1p. |
| GO:0016787 hydrolase activity | IEA GO_REF:0000002 | MODIFY | Summary: InterPro2GO maps the metallo-dependent phosphatase domain to generic hydrolase activity. Reason: Hydrolase activity is far less informative than Ppn1's two supported polyphosphate hydrolase reactions: endopolyphosphatase and exopolyphosphatase. Proposed replacements: endopolyphosphatase activity exopolyphosphatase activity Supporting Evidence: file:genes/yeast/PPN1/PPN1-uniprot.txt Has both exopolyphosphatase and endopolyphosphatase activities at different ratios depending on divalent cations |
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Download this section (compressed HTML)Q: Does Ppn1 protein itself enter the nucleus under stationary-to-active growth transitions, or does the PPN1 mutant eliminate nuclear exopolyphosphatase activity indirectly?
Q: Do the Co2+-favored exopolyphosphatase and Mg2+/ADP/arginine-favored endopolyphosphatase regimes measured with purified Ppn1 occur in the vacuolar and cytosolic compartments in vivo?
Experiment: Use endogenously tagged Ppn1, nuclear fractionation controls, and a catalytically inactive Ppn1 mutant through the stationary-to-budding shift to test whether the nuclear exopolyphosphatase activity is carried by Ppn1 itself.
Experiment: Quantify polyphosphate chain-length distributions in vacuole-enriched and cytosolic fractions of ppn1, ppn2, ppx1 and ddp1 mutant combinations across Mg2+, Co2+, phosphate and glucose shifts to connect the purified Ppn1 activity switch with in vivo flux.
Dual endo- and exopolyphosphatase with a role in phosphate metabolism; acts as both an endopolyphosphatase cleaving long chains of polyphosphate distributively to generate shorter polymer chains and as an exopolyphosphatase catalyzing the hydrolysis of terminal phosphate from polyphosphate; localizes to the vacuole, nucleus and cytosol; functions as a homodimer; relocalizes from vacuole to cytoplasm upon DNA replication stress
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