PANK4 is a two-domain cytoplasmic enzyme of the pantothenate kinase family. Its N-terminal type II pantothenate-kinase-like domain is catalytically degenerate: PANK4 has no pantothenate kinase activity and is a 'pseudo-pantothenate kinase'. Its functional activity resides in the C-terminal damage-control (DUF89) domain, a metal-dependent (Mg2+/Mn2+) phosphatase that dephosphorylates 4'-phosphopantetheine and related metabolites (e.g. pantetheine-phosphate sulfonate). Through this 4'-phosphopantetheine phosphatase activity PANK4 participates in coenzyme-A pathway homeostasis / metabolite repair. It is widely expressed, with high levels in muscle, and forms homodimers. PANK4 thus illustrates a domain-swap pseudoenzyme: a dead ancestral catalytic domain alongside a retained, distinct enzymatic activity.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004594 pantothenate kinase activity | IBA NOT GO_REF:0000033 | ACCEPT | Summary: NOT (negated): PANK4 does NOT have pantothenate kinase activity. Although it belongs to the type II pantothenate kinase family, its kinase domain is degenerate; PANK4 is a 'pseudo-pantothenate kinase'. Reason: Correct, well-supported negation (IMP, PMID:30927326 'pseudo-pantothenate kinase'). The CAUTION flags the degenerate PanK domain. Retain. Supporting Evidence: PMID:30927326 Human pantothenate kinase 4 is a pseudo-pantothenate kinase |
| GO:0005634 nucleus | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Nucleus (IBA, is_active_in). UniProt records PANK4 as cytoplasmic; the nuclear assignment is a phylogenetic inference not corroborated by the curated subcellular location. Reason: Likely over-propagated by IBA. PANK4 is reported cytoplasmic (UniProt); keep as non-core pending direct evidence rather than asserting it as a core location. Supporting Evidence: file:human/PANK4/PANK4-uniprot.txt Cytoplasm |
| GO:0005829 cytosol | IBA GO_REF:0000033 | ACCEPT | Summary: Cytosol (IBA), consistent with the curated cytoplasmic localization. Reason: Correct core localization. Supporting Evidence: file:human/PANK4/PANK4-uniprot.txt Cytoplasm |
| GO:0016791 phosphatase activity | IBA GO_REF:0000033 | ACCEPT | Summary: Phosphatase activity: PANK4's C-terminal damage-control (DUF89) domain is a metal-dependent phosphatase that dephosphorylates 4'-phosphopantetheine (and related metabolites), a metabolite-repair / CoA-pathway regulatory activity. Reason: Core molecular function with direct experimental support (EXP, PMID:27322068; UniProt RecName '4'-phosphopantetheine phosphatase'). This is the protein's real activity, distinct from the dead PanK domain. Supporting Evidence: file:human/PANK4/PANK4-uniprot.txt Phosphatase which shows a preference for 4'- |
| GO:0005524 ATP binding | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: ATP binding (IEA) from the (degenerate) pantothenate-kinase domain signature. Reason: Plausible nucleotide binding by the kinase-like fold, but not the demonstrated catalytic activity (which is metal-dependent phosphatase). Non-core. |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | ACCEPT | Summary: Cytoplasm (IEA). Reason: Correct, matches UniProt. Supporting Evidence: file:human/PANK4/PANK4-uniprot.txt Cytoplasm |
| GO:0015937 coenzyme A biosynthetic process | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: Coenzyme A biosynthetic process (IEA): PANK4's 4'-phosphopantetheine phosphatase activity acts on a CoA-pathway intermediate (metabolite repair / regulation). Reason: Correct pathway association via the phosphatase activity, but PANK4 modulates rather than performs core CoA biosynthesis; non-core. |
| GO:0015939 pantothenate metabolic process | TAS Reactome:R-HSA-199220 | KEEP AS NON CORE | Summary: Pantothenate metabolic process (TAS), pathway context (CoA/pantothenate). Reason: Pathway-level association; non-core. |
| GO:0016791 phosphatase activity | EXP PMID:27322068 A family of metal-dependent phosphatases implicated in metab... | ACCEPT | Summary: Phosphatase activity: PANK4's C-terminal damage-control (DUF89) domain is a metal-dependent phosphatase that dephosphorylates 4'-phosphopantetheine (and related metabolites), a metabolite-repair / CoA-pathway regulatory activity. Reason: Core molecular function with direct experimental support (EXP, PMID:27322068; UniProt RecName '4'-phosphopantetheine phosphatase'). This is the protein's real activity, distinct from the dead PanK domain. Supporting Evidence: file:human/PANK4/PANK4-uniprot.txt Phosphatase which shows a preference for 4'- |
| GO:0005737 cytoplasm | ISS GO_REF:0000024 | ACCEPT | Summary: Cytoplasm (ISS). Reason: Consistent core localization. Supporting Evidence: file:human/PANK4/PANK4-uniprot.txt Cytoplasm |
| GO:0004594 pantothenate kinase activity | IMP NOT PMID:30927326 Human pantothenate kinase 4 is a pseudo-pantothenate kinase. | ACCEPT | Summary: NOT (negated): PANK4 does NOT have pantothenate kinase activity. Although it belongs to the type II pantothenate kinase family, its kinase domain is degenerate; PANK4 is a 'pseudo-pantothenate kinase'. Reason: Correct, well-supported negation (IMP, PMID:30927326 'pseudo-pantothenate kinase'). The CAUTION flags the degenerate PanK domain. Retain. Supporting Evidence: PMID:30927326 Human pantothenate kinase 4 is a pseudo-pantothenate kinase |
| GO:0005829 cytosol | TAS Reactome:R-HSA-9837419 | ACCEPT | Summary: Cytosol (TAS). Reason: Consistent core localization. |
Loading supporting content…
Download this section (compressed HTML)Q: What is the precise physiological substrate spectrum of PANK4's phosphatase activity, and does it regulate CoA levels in vivo (e.g. in muscle)?
Experiment: Measure 4'-phosphopantetheine and CoA levels in PANK4-knockout vs wild-type cells/tissues, with rescue by phosphatase-dead PANK4.
Hypothesis: PANK4 phosphatase activity regulates intracellular CoA/4'-phosphopantetheine pools.
Loading supporting content…
Download this section (compressed HTML)