Pyruvate kinase 2 (Pyk2, YOR347C) is the minor pyruvate kinase isoenzyme of Saccharomyces cerevisiae (EC 2.7.1.40), a homotetrameric Mg2+/K+-dependent enzyme of the pyruvate kinase family that transfers the phosphoryl group of phosphoenolpyruvate to ADP, producing pyruvate and ATP in the last step of glycolysis. Unlike the major isoenzyme Cdc19/Pyk1, Pyk2 is not activated by fructose-1,6-bisphosphate, is subject to glucose repression and is expressed at much lower levels; when overexpressed it can fully replace Pyk1 activity. It is thought to supply pyruvate kinase activity under conditions of low glycolytic flux, such as respiratory or gluconeogenic growth. Pyk2 is a soluble cytosolic protein; a small fraction of glycolytic activity, including pyruvate kinase, co-purifies with mitochondria.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000287 magnesium ion binding | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: InterPro pyruvate kinase signatures (IPR001697, IPR015793) map to Mg2+ binding. Pyk2 is a canonical pyruvate kinase and, like all members of the family, requires a divalent cation; UniProt records Mg2+ as cofactor by similarity only. Reason: Correct cofactor binding inferred from family; part of the catalytic mechanism rather than a separate function. Supporting Evidence: file:yeast/PYK2/PYK2-uniprot.txt Name=Mg(2+); Xref=ChEBI:CHEBI:18420; Evidence={ECO:0000250}; file:yeast/PYK2/PYK2-uniprot.txt Reaction=pyruvate + ATP = phosphoenolpyruvate + ADP + H(+); |
| GO:0004743 pyruvate kinase activity | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA from the eukaryotic/bacterial pyruvate kinase node PTN000212670, whose experimental donors include yeast Cdc19/Pyk1 and Pyk2 themselves. Pyk2 retains the full PK fold and has demonstrated activity, so inheritance of the ancestral activity is sound. Supporting Evidence: file:yeast/PYK2/PYK2-uniprot.txt Reaction=pyruvate + ATP = phosphoenolpyruvate + ADP + H(+); PMID:9139918 it encodes a second functional pyruvate kinase isoenzyme, Pyk2p |
| GO:0004743 pyruvate kinase activity | IEA GO_REF:0000120 | ACCEPT | Summary: EC 2.7.1.40 / RHEA:18157 and InterPro PK signatures mapped to pyruvate kinase activity; correct for Pyk2, which is an active PK isoenzyme. Supporting Evidence: file:yeast/PYK2/PYK2-uniprot.txt Reaction=pyruvate + ATP = phosphoenolpyruvate + ADP + H(+); PMID:9139918 Overexpression of the YOR347c/PYK2 gene on a multicopy vector restored growth on glucose of a yeast pyruvate kinase 1 (pyk1) mutant strain and could completely substitute for the PYK1-encoded enzymatic activity |
| GO:0004743 pyruvate kinase activity | IGI PMID:21907146 Pyruvate kinase triggers a metabolic feedback loop that cont... | ACCEPT | Summary: IGI with CDC19/PYK1 (P00549): Gruning et al. built pyk1 pyk2 double-deletion strains rescued by ectopic PYK1 or PYK2 and measured total PK activity; PYK2-only strains have measurable but lower PK activity. Supporting Evidence: PMID:21907146 By expressing either Pyk1p or Pyk2p under the control of either a strong (TEF1) or a weak (CYC1) constitutive promoter in yeast strains deleted for both endogenous loci, we generated four yeast strains with different PYK activities. PMID:21907146 As expected, activity in PYK2-expressing cells was lower: the TEF1pr-PYK2 strain had 22% and the CYCpr-PYK2 strain 5% activity |
| GO:0004743 pyruvate kinase activity | IMP PMID:9139918 Characterization of a glucose-repressed pyruvate kinase (Pyk... | ACCEPT | Summary: Boles et al. showed that YOR347c/PYK2 encodes a functional PK isoenzyme that fully substitutes for PYK1 activity when overexpressed, and that pyk2 deletion aggravates the pyk1 phenotype; the enzyme is FBP-insensitive. Supporting Evidence: PMID:9139918 it encodes a second functional pyruvate kinase isoenzyme, Pyk2p PMID:9139918 Overexpression of the YOR347c/PYK2 gene on a multicopy vector restored growth on glucose of a yeast pyruvate kinase 1 (pyk1) mutant strain and could completely substitute for the PYK1-encoded enzymatic activity PMID:9139918 Pyk2p is active without fructose-1,6-bisphosphate |
| GO:0004743 pyruvate kinase activity | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA (GLUCFERMEN-PWY, superpathway of glucose fermentation) assigns the PEP -> pyruvate step (EC 2.7.1.40) to Pyk2. The activity is experimentally established, so the RCA activity assertion is correct. Supporting Evidence: file:yeast/PYK2/PYK2-uniprot.txt Reaction=pyruvate + ATP = phosphoenolpyruvate + ADP + H(+); PMID:9139918 it encodes a second functional pyruvate kinase isoenzyme, Pyk2p |
| GO:0004743 pyruvate kinase activity | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA (GLYCOLYSIS, glycolysis I from glucose 6-phosphate) assigns pyruvate kinase activity to Pyk2; correct, Pyk2 is the minor, glucose-repressed PK isoenzyme. Supporting Evidence: file:yeast/PYK2/PYK2-uniprot.txt Reaction=pyruvate + ATP = phosphoenolpyruvate + ADP + H(+); PMID:9139918 PYK2 gene expression is subject to glucose repression |
| GO:0005737 cytoplasm | HDA PMID:14562095 Global analysis of protein localization in budding yeast. | ACCEPT | Summary: Genome-wide GFP-fusion localization (Huh et al.) placed Pyk2-GFP in the cytoplasm, consistent with a soluble glycolytic enzyme. Supporting Evidence: PMID:14562095 Here we describe the construction and analysis of a collection of yeast strains expressing full-length, chromosomally tagged green fluorescent protein fusion proteins. |
| GO:0005737 cytoplasm | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA is_active_in cytoplasm for the pyruvate kinase clade; Pyk2 lacks targeting signals and is a soluble cytosolic enzyme (HDA GFP data agree). Supporting Evidence: PMID:14562095 Here we describe the construction and analysis of a collection of yeast strains expressing full-length, chromosomally tagged green fluorescent protein fusion proteins. file:yeast/PYK2/PYK2-uniprot.txt Reaction=pyruvate + ATP = phosphoenolpyruvate + ADP + H(+); |
| GO:0005739 mitochondrion | IDA PMID:16962558 Enolase takes part in a macromolecular complex associated to... | KEEP AS NON CORE | Summary: Brandina et al. used enzyme assays on purified mitochondria to show that a fraction of every glycolytic activity, including pyruvate kinase, co-purifies with the mitochondrial outer surface. Activity assays alone cannot distinguish Pyk1 from Pyk2; this is a peripheral association, not the site of its core activity. Reason: Experimental (abstract-only; curator saw full text) so not removed, but mitochondrial association is peripheral to the cytosolic glycolytic function. Supporting Evidence: PMID:16962558 we show that all glycolytic enzymes are associated with mitochondria in yeast PMID:16962558 The identified components included additional glycolytic enzymes |
| GO:0005829 cytosol | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA is_active_in cytosol for the glucose-fermentation superpathway step; correct site of Pyk2 activity. Supporting Evidence: PMID:14562095 Here we describe the construction and analysis of a collection of yeast strains expressing full-length, chromosomally tagged green fluorescent protein fusion proteins. file:yeast/PYK2/PYK2-uniprot.txt Reaction=pyruvate + ATP = phosphoenolpyruvate + ADP + H(+); |
| GO:0005829 cytosol | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA is_active_in cytosol for glycolysis I; correct site of Pyk2 activity. Supporting Evidence: PMID:14562095 Here we describe the construction and analysis of a collection of yeast strains expressing full-length, chromosomally tagged green fluorescent protein fusion proteins. file:yeast/PYK2/PYK2-uniprot.txt Reaction=pyruvate + ATP = phosphoenolpyruvate + ADP + H(+); |
| GO:0006096 glycolysis | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA for glycolysis from the PK clade; Pyk2 catalyses the final, ATP-generating step of glycolysis. Supporting Evidence: file:yeast/PYK2/PYK2-uniprot.txt PATHWAY: Carbohydrate degradation; glycolysis; pyruvate from D- PMID:9139918 Overexpression of the YOR347c/PYK2 gene on a multicopy vector restored growth on glucose of a yeast pyruvate kinase 1 (pyk1) mutant strain and could completely substitute for the PYK1-encoded enzymatic activity |
| GO:0006096 glycolysis | IEA GO_REF:0000120 | ACCEPT | Summary: UniPathway UPA00109 / InterPro mapping to glycolysis; correct for an active PK isoenzyme. Supporting Evidence: file:yeast/PYK2/PYK2-uniprot.txt PATHWAY: Carbohydrate degradation; glycolysis; pyruvate from D- PMID:9139918 it encodes a second functional pyruvate kinase isoenzyme, Pyk2p |
| GO:0006096 glycolysis | IMP PMID:9139918 Characterization of a glucose-repressed pyruvate kinase (Pyk... | ACCEPT | Summary: Boles et al.: PYK2 restores glucose growth of pyk1 mutants and pyk1 pyk2 double mutants are more severely impaired; Pyk2 contributes to glycolytic flux under low-flux (derepressed) conditions. Supporting Evidence: PMID:9139918 Overexpression of the YOR347c/PYK2 gene on a multicopy vector restored growth on glucose of a yeast pyruvate kinase 1 (pyk1) mutant strain and could completely substitute for the PYK1-encoded enzymatic activity PMID:9139918 the growth defects of a pyk1 pyk2 double-deletion strain were even more pronounced than those of a pyk1 single-mutation strain PMID:9139918 The results indicate that the PYK2-encoded pyruvate kinase may be used under conditions of very low glycolytic flux |
| GO:0019658 bifid shunt | RCA GO_REF:0000123 | REMOVE | Summary: YeastPathways RCA from GLUCFERMEN-PWY mapped to GO bifid shunt, the Bifidobacterium phosphoketolase-based heterofermentation of glucose to lactate and acetate. S. cerevisiae has no bifid shunt; Pyk2 participates in glycolysis/alcoholic fermentation. Reason: Mis-mapped pathway: bifid shunt does not occur in S. cerevisiae. Supporting Evidence: PMID:9139918 it encodes a second functional pyruvate kinase isoenzyme, Pyk2p |
| GO:0030955 potassium ion binding | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: InterPro PK signatures map to potassium ion binding. Pyruvate kinases are K+-activated; UniProt lists K+ as a cofactor by similarity. Correct for the family, non-core. Reason: Cofactor binding inferred from family; part of catalytic mechanism. Supporting Evidence: file:yeast/PYK2/PYK2-uniprot.txt Name=K(+); Xref=ChEBI:CHEBI:29103; Evidence={ECO:0000250}; |
| GO:0032787 monocarboxylic acid metabolic process | IEA GO_REF:0000117 | MARK AS OVER ANNOTATED | Summary: ARBA rule assigns the very broad monocarboxylic acid metabolic process. Pyruvate is a monocarboxylate, so this is not false, but it adds nothing over glycolysis and is not how Pyk2 function should be described. Reason: Uninformative high-level process; glycolysis captures the role. Supporting Evidence: file:yeast/PYK2/PYK2-uniprot.txt Reaction=pyruvate + ATP = phosphoenolpyruvate + ADP + H(+); |
| GO:0061620 obsolete glycolytic process through glucose-6-phosphate | RCA GO_REF:0000123 | MODIFY | Summary: YeastPathways RCA (GLYCOLYSIS) to glycolytic process through glucose-6-phosphate, which is now obsolete and replaced by glycolysis (GO:0006096). Pyk2 does act in glycolysis. Reason: Obsolete term; replace with GO:0006096 per its replaced_by. Proposed replacements: glycolysis Supporting Evidence: PMID:9139918 Overexpression of the YOR347c/PYK2 gene on a multicopy vector restored growth on glucose of a yeast pyruvate kinase 1 (pyk1) mutant strain and could completely substitute for the PYK1-encoded enzymatic activity |
| GO:1904408 melatonin binding | IDA PMID:31708896 Glycolytic Proteins Interact With Intracellular Melatonin in... | MARK AS OVER ANNOTATED | Summary: Morcillo-Parra et al. pulled down intracellular melatonin-binding proteins with anti-melatonin IgG beads during fermentation and identified glycolytic enzymes by MS, including Pyk2 (band a). This is an affinity co-purification; neither a binding site nor a physiological consequence for pyruvate kinase is established. Reason: Affinity co-purification of an abundant glycolytic enzyme is weak support for a specific melatonin-binding activity; the experimental report is retained but likely overstates a physiologic molecular function. Supporting Evidence: PMID:31708896 Surprisingly, most of the proteins identified participate in the glycolytic pathway: pyruvate kinase 1 (Pyk2p; band a), enolase (Eno1p, Eno2p; band c), fructose biphosphate aldolase (Fba1p; band d), and glyceraldehyde-3-phosphate dehydrogenase (Tdh1p, Tdh2p, Tdh3p; band f). PMID:31708896 We subsequently performed immunopurification melatonin-IgG-Dynabeads and identified a set of proteins that interact with melatonin inside the cell. |
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Download this section (compressed HTML)Q: Under which physiological conditions (e.g. diauxic shift, growth on ethanol/glycerol) does Pyk2 carry a significant fraction of PEP-to-pyruvate flux, and does its FBP insensitivity prevent futile cycling with PEP carboxykinase?
Q: Do Cdc19 and Pyk2 form mixed hetero-tetramers in vivo when co-expressed?
Experiment: 13C flux analysis in pyk2-deleted versus wild-type cells during growth on ethanol or in glucose-limited chemostats, combined with targeted proteomics of Pyk1/Pyk2 levels, to quantify the in vivo contribution of Pyk2.
Pyruvate kinase; appears to be modulated by phosphorylation; transcription repressed by glucose, and Pyk2p may be active under low glycolytic flux; PYK2 has a paralog, CDC19, that arose from the whole genome duplication
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