PDSS2 (decaprenyl-diphosphate synthase subunit 2; also DLP1/hDLP1) is one of the two subunits of the human all-trans-decaprenyl-diphosphate synthase, a mitochondrial trans-prenyltransferase. Together with PDSS1 it forms a 2:2 heterotetramer that condenses (2E,6E)-farnesyl diphosphate (the primer) with seven isopentenyl diphosphate units to build all-trans-decaprenyl diphosphate, the C50 polyprenyl side chain of coenzyme Q10 (ubiquinone-10). This is the first committed step in assembly of the ubiquinone side chain and occurs in the mitochondrial matrix / inner membrane. The catalytic activity is a property of the assembled complex; PDSS2 is not active on its own but is required, alongside PDSS1, for determining the final isoprenoid chain length (Q9 versus Q10). Loss-of-function variants cause primary coenzyme Q10 deficiency type 3 (COQ10D3), an encephalomyopathy that can present as Leigh syndrome with nephrotic syndrome. PDSS2 belongs to the FPP/GGPP synthase (polyprenyl synthetase) family.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004659 prenyltransferase activity | IBA GO_REF:0000033 | MODIFY | Summary: General prenyltransferase (transferase transferring prenyl groups) activity inferred phylogenetically. Correct in kind but too general - the specific, experimentally supported activity of the PDSS1/PDSS2 complex is the all-trans-decaprenyl-diphosphate synthase reaction (GO:0097269), and the enzyme is a subunit that contributes to, rather than independently enables, that activity. Reason: The generic prenyltransferase term should be replaced by the specific decaprenyl-diphosphate synthase activity that is documented for this enzyme. Proposed replacements: all-trans-decaprenyl-diphosphate synthase activity |
| GO:0005739 mitochondrion | IBA GO_REF:0000033 | ACCEPT | Summary: Mitochondrial localization inferred phylogenetically, consistent with the experimentally supported human mitochondrial localization and with the ubiquinone biosynthesis pathway operating in mitochondria. Supporting Evidence: file:human/PDSS2/PDSS2-uniprot.txt SUBCELLULAR LOCATION: Mitochondrion |
| GO:0006744 ubiquinone biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: Involvement in ubiquinone (coenzyme Q) biosynthesis inferred phylogenetically. This is the core biological process for PDSS2 - the enzyme builds the decaprenyl side chain of ubiquinone-10, and UniProt assigns the "Cofactor biosynthesis; ubiquinone biosynthesis" pathway. Supporting Evidence: file:human/PDSS2/PDSS2-uniprot.txt PATHWAY: Cofactor biosynthesis; ubiquinone biosynthesis. |
| GO:0008299 isoprenoid biosynthetic process | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Isoprenoid biosynthetic process is a true but more general parent of the specific ubiquinone side-chain (polyprenyl) biosynthesis carried out by PDSS2. Correct but not the most informative core process; retained as non-core in favor of the ubiquinone biosynthetic process term. Reason: General isoprenoid-biosynthesis parent; the informative core process is ubiquinone biosynthetic process (GO:0006744). |
| GO:0032476 polyprenyl diphosphate synthase complex | IBA GO_REF:0000033 | MODIFY | Summary: Correctly places PDSS2 in a polyprenyl diphosphate synthase complex, but the more specific term is available - the human enzyme is a heterotetramer of 2 PDSS1 and 2 PDSS2 subunits, matching GO:0032478 "heterotetrameric polyprenyl diphosphate synthase complex". Reason: A more specific complex term (heterotetrameric) is supported by the experimental subunit stoichiometry. Proposed replacements: heterotetrameric polyprenyl diphosphate synthase complex |
| GO:0004659 prenyltransferase activity | IEA GO_REF:0000002 | MODIFY | Summary: InterPro2GO mapping (IPR000092, polyprenyl synthetase domain) to the generic prenyltransferase activity. Correct at the domain-family level but less informative than the specific decaprenyl-diphosphate synthase activity supported experimentally for this protein. Reason: Replace the generic domain-based prenyltransferase term with the specific characterized activity. Proposed replacements: all-trans-decaprenyl-diphosphate synthase activity |
| GO:0005739 mitochondrion | IEA GO_REF:0000044 | ACCEPT | Summary: Mitochondrial localization from UniProt Swiss-Prot subcellular-location mapping, matching the curated UniProt SUBCELLULAR LOCATION and the ubiquinone biosynthesis compartment. Supporting Evidence: file:human/PDSS2/PDSS2-uniprot.txt SUBCELLULAR LOCATION: Mitochondrion |
| GO:0006629 lipid metabolic process | IEA GO_REF:0000117 | MARK AS OVER ANNOTATED | Summary: ARBA machine-learning annotation to the very broad "lipid metabolic process". While ubiquinone/isoprenoid metabolism is technically lipid metabolism, this term is far more general than the specific ubiquinone and isoprenoid biosynthetic processes already annotated, and adds no informative content. Reason: Overly general ancestor term superseded by the specific ubiquinone biosynthetic process annotation. |
| GO:0008299 isoprenoid biosynthetic process | IEA GO_REF:0000120 | KEEP AS NON CORE | Summary: Electronic annotation to isoprenoid biosynthetic process, a true but general parent of the ubiquinone side-chain (polyprenyl) biosynthesis. Kept as non-core in favor of the specific ubiquinone biosynthetic process term. Reason: General isoprenoid-biosynthesis parent; core process is ubiquinone biosynthesis. |
| GO:0097269 all-trans-decaprenyl-diphosphate synthase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Electronic annotation to the specific decaprenyl-diphosphate synthase activity (from RHEA:27802 / EC:2.5.1.91). This is exactly the reaction curated by UniProt with experimental evidence, so the term is correct. Strictly the activity is a property of the assembled PDSS1/PDSS2 complex (the experimental annotation uses contributes_to), but accepting this MF is appropriate. Supporting Evidence: file:human/PDSS2/PDSS2-uniprot.txt all-trans-decaprenyl diphosphate + 7 diphosphate |
| GO:0006744 ubiquinone biosynthetic process | IEA GO_REF:0000120 | ACCEPT | Summary: Electronic annotation to ubiquinone biosynthetic process, the core pathway for PDSS2, consistent with the UniProt pathway assignment and the experimental IDA annotation from PMID:16262699. Supporting Evidence: file:human/PDSS2/PDSS2-uniprot.txt PATHWAY: Cofactor biosynthesis; ubiquinone biosynthesis. |
| GO:0021549 cerebellum development | IEA GO_REF:0000107 | KEEP AS NON CORE | Summary: Automatic Ensembl-Compara transfer from the mouse ortholog (Q33DR3) of a possible role in cerebellar development. UniProt records this only as a "By similarity" possibility, and any cerebellar phenotype is plausibly a downstream consequence of impaired CoQ10 biosynthesis rather than a distinct molecular role. Retained as a non-core, ortholog-inferred developmental association. Reason: Ortholog-transferred "may play a role" developmental association, not a core molecular function; likely downstream of CoQ10 deficiency. |
| GO:0032478 heterotetrameric polyprenyl diphosphate synthase complex | IEA GO_REF:0000107 | ACCEPT | Summary: Electronic (Ensembl-Compara) annotation placing PDSS2 in the heterotetrameric polyprenyl diphosphate synthase complex. This matches the experimentally determined 2 PDSS1 + 2 PDSS2 heterotetramer and the parallel IDA annotation from PMID:16262699. Supporting Evidence: file:human/PDSS2/PDSS2-uniprot.txt Heterotetramer composed of 2 PDSS1/DPS1 and 2 PDSS2/DLP1 subunits. |
| GO:0005829 cytosol | IDA GO_REF:0000052 | MARK AS OVER ANNOTATED | Summary: HPA immunofluorescence-based cytosolic localization. This conflicts with the curated mitochondrial (matrix/inner-membrane) localization that is supported by the mitochondrial proteome data, the UniProt SUBCELLULAR LOCATION, and the N-terminal mitochondrial-targeting presequence, and with the ubiquinone biosynthesis pathway operating in mitochondria. Treated as an over-annotation (single-antibody IF can mislocalize matrix proteins); not removed because it is an experimental (IDA) annotation. Reason: Cytosolic IF localization conflicts with the well-supported mitochondrial localization; likely an antibody/IF artifact. |
| GO:0005739 mitochondrion | HTP PMID:34800366 Quantitative high-confidence human mitochondrial proteome an... | ACCEPT | Summary: High-throughput identification of PDSS2 in the high-confidence human mitochondrial proteome, corroborating the mitochondrial localization of this ubiquinone-biosynthesis enzyme. |
| GO:0097269 all-trans-decaprenyl-diphosphate synthase activity | IDA PMID:16262699 Characterization of solanesyl and decaprenyl diphosphate syn... | ACCEPT | Summary: Experimental (IDA) annotation with the contributes_to qualifier - correct framing, because decaprenyl-diphosphate synthase activity is a property of the assembled PDSS1/PDSS2 heterotetramer and PDSS2 contributes to it rather than catalyzing alone. Saiki et al. reconstituted hDPS1 (PDSS1) + hDLP1 (PDSS2) in E. coli, obtained Q10, and verified in vitro decaprenyl diphosphate synthase activity. This is a core molecular function. Supporting Evidence: PMID:16262699 an in vitro activity of solanesyl or decaprenyl diphosphate synthase was verified |
| GO:0032478 heterotetrameric polyprenyl diphosphate synthase complex | IDA PMID:16262699 Characterization of solanesyl and decaprenyl diphosphate syn... | ACCEPT | Summary: Experimental (IDA) annotation of PDSS2 as part of the heterotetrameric polyprenyl diphosphate synthase complex. Saiki et al. showed by gel-filtration that the human long-chain trans-prenyl diphosphate synthase is a heterotetramer of hDPS1 (PDSS1) and hDLP1 (PDSS2). Core complex membership. Supporting Evidence: PMID:16262699 they consist of heterotetramers |
| GO:0021549 cerebellum development | ISS GO_REF:0000024 | KEEP AS NON CORE | Summary: Sequence-similarity (ISS) transfer from the mouse ortholog (Q33DR3) of a possible cerebellar-development role. As with the parallel IEA annotation, this reflects UniProt's "may play a role during cerebellar development (By similarity)" and is not a demonstrated human molecular function; any cerebellar phenotype is most likely downstream of CoQ10 deficiency. Retained as non-core. Reason: Ortholog-inferred developmental association, not a core function. |
| GO:0005515 protein binding | IPI PMID:16262699 Characterization of solanesyl and decaprenyl diphosphate syn... | MARK AS OVER ANNOTATED | Summary: IPI annotation (WITH UniProtKB:Q5T2R2 = PDSS1) capturing the PDSS2-PDSS1 interaction. The interaction is real and functionally central, but the bare "protein binding" term is uninformative; the meaningful representation is PDSS2's membership in the PDSS1/PDSS2 heterotetramer (GO:0032478), which is already annotated. Marked as over-annotated rather than removed (experimental IPI). Reason: Uninformative "protein binding"; the PDSS1 interaction is better captured by heterotetrameric complex membership. |
| GO:0005759 mitochondrial matrix | TAS Reactome:R-HSA-2162253 | ACCEPT | Summary: Reactome (TAS) places the PDSS1,2-catalyzed FPP + IPP condensation in the mitochondrial matrix. Consistent with the mitochondrial localization of the enzyme and a reasonable, more specific subcompartment assignment for where the reaction occurs. Supporting Evidence: Reactome:R-HSA-2162253 to form the polyisoprenoid tail, all-trans-decaprenyl diphosphate |
| GO:0006744 ubiquinone biosynthetic process | IDA PMID:16262699 Characterization of solanesyl and decaprenyl diphosphate syn... | ACCEPT | Summary: Experimental (IDA) annotation to ubiquinone biosynthetic process. Saiki et al. showed that co-expression of PDSS1 and PDSS2 produces ubiquinone-10 in E. coli, directly demonstrating the enzyme's role in synthesizing the ubiquinone side chain. Core biological process. Supporting Evidence: PMID:16262699 double transformants expressing mSPS1 and mDLP1 or hDPS1 and hDLP1 produced Q9 or Q10, respectively |
| GO:0008299 isoprenoid biosynthetic process | IDA PMID:16262699 Characterization of solanesyl and decaprenyl diphosphate syn... | KEEP AS NON CORE | Summary: Experimental (IDA) annotation to isoprenoid biosynthetic process. The decaprenyl diphosphate product is a polyisoprenoid, so this is correct, but it is a more general parent of the specific ubiquinone side-chain biosynthesis. Retained as non-core in favor of the ubiquinone biosynthetic process term. Reason: General isoprenoid-biosynthesis parent of the specific ubiquinone process. |
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Download this section (compressed HTML)Q: Is PDSS2 required only for chain-length determination, or does it also carry part of the catalytic machinery of the heterotetramer?
Q: Does the reported cerebellar-development role reflect a molecular function of PDSS2 distinct from its role in CoQ10 biosynthesis, or is it entirely a downstream consequence of ubiquinone deficiency?
Experiment: Reconstitute the human PDSS1/PDSS2 heterotetramer and test defined active-site and interface mutants (including the COQ10D3 S382L variant) for decaprenyl diphosphate synthase activity and chain-length output.
Experiment: Determine the submitochondrial localization (matrix versus inner-membrane association) of the PDSS1/PDSS2 complex by fractionation and proximity labeling to resolve the matrix versus inner-membrane assignment.
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