Lanthanide-dependent pyrroloquinoline quinone (PQQ)-dependent alcohol dehydrogenase that catalyzes periplasmic oxidation of diverse aliphatic and aromatic alcohols. PedH requires usable trivalent lanthanides for catalysis and is the metal-conditioned counterpart of calcium-dependent PedE. PedS2/PedR2 signaling and an unresolved positive input favor pedH expression when lanthanides are available; its physiological cytochrome c electron-transfer partner in KT2440 has not been directly established.
Definition: Binding to a lanthanide ion, including lanthanum (La3+), cerium (Ce3+), praseodymium (Pr3+), neodymium (Nd3+), and samarium (Sm3+). Lanthanides are f-block elements with unique chemical properties distinct from transition metals.
Justification: Many bacterial enzymes specifically require lanthanides rather than calcium or other metals. Current GO only has generic "metal ion binding" which fails to capture this specificity.
Definition: Catalysis of the oxidation of alcohols to aldehydes or ketones with the concomitant reduction of an electron acceptor, requiring lanthanide ions for activity.
Justification: Distinguishes lanthanide-dependent enzymes from calcium-dependent PQQ dehydrogenases, which is functionally and evolutionarily significant.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005509 calcium ion binding | IEA GO_REF:0000120 | REMOVE | Summary: Incorrect annotation. PedH is lanthanide-dependent, not calcium-dependent. This annotation likely arose from sequence similarity to other PQQ dehydrogenases. PedH requires La3+, Ce3+, Pr3+, Nd3+, Sm3+ etc. for activity, but not Ca2+. |
| GO:0016020 membrane | IEA GO_REF:0000002 | REMOVE | Summary: Too vague and potentially misleading. PedH is a periplasmic protein, not membrane-associated. While it has a signal peptide for periplasmic targeting, it is a soluble enzyme in the periplasm, not membrane-bound. |
| GO:0016614 oxidoreductase activity, acting on CH-OH group of donors | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: Accurate but too general. This correctly describes the broad enzymatic activity but lacks specificity about the PQQ-dependence and cytochrome c as electron acceptor. The more specific term GO:0052934 is present and preferred. |
| GO:0030288 outer membrane-bounded periplasmic space | IEA GO_REF:0000002 | REMOVE | Summary: Less accurate than GO:0042597. While PedH is in the periplasm, this term implies specific association with the outer membrane boundary. Bioinformatics analysis confirms PedH is a soluble enzyme (no TM regions in mature protein) that functions throughout the periplasmic space, not specifically at membrane interfaces. The hydrophobic region (aa 6-27) is the signal peptide, cleaved upon export. Proposed replacements: periplasmic space |
| GO:0016491 oxidoreductase activity | IEA GO_REF:0000120 | REMOVE | Summary: Too general and uninformative. While technically correct, this term provides no specific functional information. The more specific terms GO:0052934 and GO:0016614 are present and much more informative. |
| GO:0020037 heme binding | IEA GO_REF:0000117 | REMOVE | Summary: Incorrect annotation. PedH is a PQQ quinoprotein rather than a heme-containing enzyme. A cytochrome c is the assigned reaction acceptor, not a prosthetic group bound by PedH. |
| GO:0042597 periplasmic space | IEA GO_REF:0000120 | ACCEPT | Summary: Correct and well-supported. PedH has a signal peptide (aa 1-25) directing export to periplasm. Bioinformatics analysis confirms no transmembrane regions in mature protein - it's a soluble enzyme functioning throughout the periplasmic space. Like all PQQ-ADHs (ExaA, PedE, MxaF, XoxF), PedH is freely diffusible in periplasm where it oxidizes alcohols and transfers electrons to cytochrome c. Supporting Evidence: file:PSEPK/pedH/pedH-deep-research-falcon.md PedH is explicitly described as part of a **periplasmic oxidation system** (together with PedE) that supports growth on alcoholic substrates |
| GO:0046872 metal ion binding | IEA GO_REF:0000043 | ACCEPT | Summary: Correct but too general. PedH specifically binds lanthanide ions (La3+, Ce3+, Pr3+, Nd3+, Sm3+) which are essential for activity. This is NOT calcium-dependent like other PQQ dehydrogenases. GO lacks a specific lanthanide binding term which would be more accurate. Falcon deep research confirms lanthanide-exclusive activity and attributes the metal selectivity to a conserved active-site Asp (vs Ser in the Ca2+-dependent paralog PedE). Supporting Evidence: file:PSEPK/pedH/pedH-deep-research-falcon.md PedH is catalytically active **only in the presence of trivalent lanthanides (Ln3+)** and is inactive with several tested heavy lanthanides/other trivalent metals. file:PSEPK/pedH/pedH-deep-research-falcon.md PedH contains a **conserved active-site Asp** (contrasting with a Ser in PedE) that is associated with **Ln3+ coordination** in lanthanide-dependent quinoprotein dehydrogenases. |
| GO:0052934 alcohol dehydrogenase (cytochrome c) activity | IEA GO_REF:0000120 | ACCEPT | Summary: Specific EC-derived annotation for PedH's core alcohol-oxidation chemistry. The purified-enzyme assays establish lanthanide-dependent alcohol dehydrogenase activity, but they used PMS/DCPIP rather than directly identifying the physiological KT2440 cytochrome c partner. Supporting Evidence: file:PSEPK/pedH/pedH-deep-research-falcon.md PedH belongs to a family of periplasmic **quinoprotein** alcohol dehydrogenases that use the redox cofactor **PQQ** to catalyze oxidation of alcohols (and in some cases aldehydes). file:PSEPK/pedH/pedH-deep-research-falcon.md It oxidizes a **broad range** of alcohol substrates, including **linear and aromatic primary and secondary alcohols**, and can show activity with some aldehydes |
| GO:0070968 pyrroloquinoline quinone binding | IEA GO_REF:0000117 | ACCEPT | Summary: Perfect annotation. PedH absolutely requires PQQ as a cofactor (1:1 stoichiometry) for all catalytic activity. This is well-supported by crystal structure data showing specific PQQ binding sites. Core molecular function. Falcon deep research classifies PedH within the periplasmic PQQ-dependent quinoprotein alcohol dehydrogenase family. Supporting Evidence: file:PSEPK/pedH/pedH-deep-research-falcon.md PedH belongs to a family of periplasmic **quinoprotein** alcohol dehydrogenases that use the redox cofactor **PQQ** to catalyze oxidation of alcohols (and in some cases aldehydes). |
| GO:0006066 alcohol metabolic process | IEA | NEW | Summary: PedH catalyzes the periplasmic oxidation of a broad range of alcohols including linear aliphatic alcohols, aromatic alcohols, and secondary alcohols. Reason: This biological process term captures PedH's primary function in alcohol catabolism, which is essential for growth on various volatile organic compounds. Supporting Evidence: PMID:28655819 efficient growth of cells with various naturally occurring alcoholic VOCs relies on the functional production of the lanthanide-dependent ADH PedH file:PSEPK/pedH/pedH-deep-research.md catalyzes the periplasmic oxidation of a broad range of alcohols including linear aliphatic alcohols, aromatic alcohols such as 2-phenylethanol, secondary alcohols |
| GO:0042537 benzene-containing compound metabolic process | IEA | NEW | Summary: PedH is central to the 2-phenylethanol degradation pathway and catalyzes the oxidation of aromatic alcohols including 2-phenylethanol to phenylacetaldehyde. Reason: This biological process term captures PedH's specific role in aromatic compound catabolism, particularly in the degradation of benzene-containing alcohols. Supporting Evidence: PMID:18177365 Another catabolic route (PedS(1)R(1)ABCS(2)R(2)DEFGHI) is needed for the uptake of 2-phenylethanol and for its oxidation to phenylacetic acid via phenylacetaldehyde. file:PSEPK/pedH/pedH-deep-research.md PedH is integral to aromatic alcohol catabolism and detoxification in Pseudomonas putida. It is part of the 2-phenylethanol degradation (Ped) pathway file:PSEPK/pedH/pedH-deep-research-falcon.md a **ΞpedH** strain fails to grow on 2-phenylethanol under conditions where the REE switch represses reliance on PedE |
| GO:0010468 regulation of gene expression | IMP PMID:28655819 Functional Role of Lanthanides in Enzymatic Activity and Tra... | NEW | Summary: PedH deletion changes pedE and pedH promoter output, establishing a non-core regulatory phenotype while leaving the molecular mechanism unresolved. Reason: A BP annotation does not imply that PedH binds DNA or has a transcription-regulator MF. Retain the genetic feedback phenotype without adding such a molecular function or placing it in the catalytic core. Supporting Evidence: PMID:28655819 PedH not only has a catalytic function but is also involved in the transcriptional regulation of pedE and pedH, most likely acting as a sensory module PMID:30158283 positive-feedback function of PedH in the presence of Ln3+ ions |
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Download this section (compressed HTML)Q: What structural features of PedH enable selective binding of lanthanides over more abundant calcium ions?
Q: How does lanthanide availability in the environment regulate the expression and activity of PedH versus calcium-dependent alcohol dehydrogenases?
Q: What is the electronic basis for the enhanced catalytic efficiency of lanthanide-PQQ complexes compared to calcium-PQQ?
Experiment: X-ray absorption spectroscopy to characterize lanthanide coordination geometry and electronic structure in the active site
Experiment: Competition assays with various lanthanides to determine binding affinity hierarchy and catalytic efficiency
Experiment: Environmental metagenomics to correlate pedH gene abundance with soil lanthanide concentrations
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