| Category | Specific findings (with numbers) | Evidence/source (first author year journal) | URL/DOI |
|---|---|---|---|
| Identity | **pedH = PP_2679 = UniProt Q88JH0** in *Pseudomonas putida* KT2440; characterized as a **lanthanide-dependent PQQ alcohol/ethanol dehydrogenase** that is inversely regulated with **PedE (PP_2674)**. (pqac-00000001, pqac-00000023) | Wehrmann 2017 *mBio*; Wehrmann 2018 *mSphere* | https://doi.org/10.1128/mbio.00570-17; https://doi.org/10.1128/msphere.00376-18 |
| Core biochemical function | Periplasmic **PQQ-dependent alcohol dehydrogenase** in a periplasmic oxidation system; catalyzes oxidation of alcohols/aldehydes important for growth on alcoholic volatiles, including **2-phenylethanol**. (pqac-00000022, pqac-00000023) | Wehrmann 2019 *Front. Microbiol.*; Wehrmann 2017 *mBio* | https://doi.org/10.3389/fmicb.2019.02494; https://doi.org/10.1128/mbio.00570-17 |
| Metal cofactor requirement | PedH is active **only with Ln³⁺**; active with **La³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Gd³⁺, Tb³⁺**; inactive with **Er³⁺, Yb³⁺, Y³⁺, Sc³⁺** under tested conditions. Peak activity reported with **Pr³⁺/Nd³⁺**. (pqac-00000002, pqac-00000007) | Wehrmann 2017 *mBio* | https://doi.org/10.1128/mbio.00570-17 |
| Substrate scope | Broad substrate range similar to PedE: **linear and aromatic primary/secondary alcohols** and some **aldehydes**; example substrates include **ethanol, 1-butanol, 2-phenylethanol, glycerol, 2,3-butanediol**. Methanol is a poor substrate. (pqac-00000007, pqac-00000021, pqac-00000024) | Wehrmann 2017 *mBio*; Wehrmann 2020 *mBio*; Liu 2021 *Front. Bioeng. Biotechnol.* | https://doi.org/10.1128/mbio.00570-17; https://doi.org/10.1128/mbio.00516-20; https://doi.org/10.3389/fbioe.2021.728767 |
| Kinetics and affinity | Under optimized assays, **Vmax ≈ 10.6 U mg⁻¹** for ethanol vs **6.1 U mg⁻¹** for PedE; **Km(ethanol) ≈ 177 µM** vs PedE **≈ 85 µM**; Ln binding **Kd ≈ 25–75 nM**, far tighter than PedE Ca²⁺ binding (**~64 µM**). PedH active from **10 nM to 100 µM Ln**, peak around **1 µM**. (pqac-00000002, pqac-00000005, pqac-00000016) | Wehrmann 2017 *mBio* | https://doi.org/10.1128/mbio.00570-17 |
| Representative specific activities | Example activities higher than PedE for several substrates: **ethanol ~11.0 vs 6.7 U mg⁻¹**, **1-butanol ~11.5 vs 5.8 U mg⁻¹** (PedH vs PedE). On glycerol, PedH **0.9 ± 0.1 U mg⁻¹** vs PedE **0.3 ± 0.1 U mg⁻¹**. (pqac-00000007, pqac-00000021, pqac-00000028) | Wehrmann 2017 *mBio*; Wehrmann 2020 *mBio* | https://doi.org/10.1128/mbio.00570-17; https://doi.org/10.1128/mbio.00516-20 |
| Localization / cell compartment | Explicitly described as part of a **periplasmic oxidation system**; PedE/PedH periplasmic oxidation contributes to detoxification/catabolism of volatile alcohols and glycerol-related metabolism. (pqac-00000021, pqac-00000022, pqac-00000023) | Wehrmann 2020 *mBio*; Wehrmann 2019 *Front. Microbiol.*; Wehrmann 2017 *mBio* | https://doi.org/10.1128/mbio.00516-20; https://doi.org/10.3389/fmicb.2019.02494; https://doi.org/10.1128/mbio.00570-17 |
| Pathway context: volatile alcohols | Expression of **either PedE or PedH is required** for efficient growth on volatile alcohols; **ΔpedH** shows impaired/no growth on **2-phenylethanol** when La³⁺ is present, consistent with the Ln switch forcing dependence on PedH. (pqac-00000001, pqac-00000002) | Wehrmann 2018 *mSphere*; Wehrmann 2017 *mBio* | https://doi.org/10.1128/msphere.00376-18; https://doi.org/10.1128/mbio.00570-17 |
| Pathway context: glycerol | PedE/PedH initiate a **novel glycerol route** parallel to **glpFKRD**: glycerol oxidation proceeds via **glyceraldehyde → glycerate**, then **GarK** phosphorylates glycerate for entry into central metabolism. Presence of PedH shortens lag on glycerol. (pqac-00000019, pqac-00000021) | Wehrmann 2020 *mBio* | https://doi.org/10.1128/mbio.00516-20 |
| Pathway context: 2,3-butanediol | PedE/PedH are responsible for **(2S,3S)-2,3-butanediol dehydrogenation to acetoin**; acetoin then enters metabolism via the **acetoin dehydrogenase enzyme system**. (pqac-00000024) | Liu 2021 *Front. Bioeng. Biotechnol.* | https://doi.org/10.3389/fbioe.2021.728767 |
| REE switch regulation | **PedS2/PedR2** is the key two-component system for the rare-earth-element switch. In **no Ln**, PedS2 phosphorylates PedR2, which **activates pedE** and **represses pedH**; with Ln, PedS2 kinase activity drops, relieving pedH repression and shifting cells toward PedH-dependent oxidation. (pqac-00000001, pqac-00000015) | Wehrmann 2018 *mSphere* | https://doi.org/10.1128/msphere.00376-18 |
| Quantitative regulation / mutants | In a **ΔpedH** background, suppressor mutations in **pedS2** restore growth with La³⁺; the **PedS2 S178P** allele gave nearly identical **pedE promoter activity with vs without La³⁺ (ratio ~0.89 ± 0.02)** and **>24-fold** higher activity than the ΔpedH parent; ΔpedH otherwise showed no growth within **72 h** under tested La³⁺ conditions. (pqac-00000000, pqac-00000013) | Wehrmann 2018 *mSphere* | https://doi.org/10.1128/msphere.00376-18 |
| Lanthanide uptake / metal homeostasis | Efficient PedH-dependent growth at low Ln requires **PedA1A2BC ABC transporter**; without it, about **~100-fold higher La³⁺** is needed for PedH-dependent growth on 2-phenylethanol. Iron, copper, and zinc alter the REE switch, likely via mismetallation/competition. (pqac-00000004, pqac-00000010) | Wehrmann 2019 *Front. Microbiol.*; Gorniak 2024 *mSphere* | https://doi.org/10.3389/fmicb.2019.02494; https://doi.org/10.1128/msphere.00685-24 |
| 2024 update: growth effects of light vs heavy Ln | In KT2440, the Ln switch is **element-specific**. **La/Ce/Nd** and an Ln mix improved growth; **heavy Ln** impaired growth. Best performance occurred at **10–50 nM La**, with **growth rate 1.64 ± 0.13 h⁻¹** and **doubling time 0.42 ± 0.03 h**, versus **0.88 ± 0.06 h⁻¹** without Ln. **Er** caused little benefit and could impair fitness. (pqac-00000036) | Gorniak 2024 *mSphere* | https://doi.org/10.1128/msphere.00685-24 |
| 2024 update: pedE/pedH transcript tuning | 2024 RNA-seq showed the switch is a **fine-tuning of pedE/pedH transcript pools**, not a binary on/off. **pedE RPKM**: **410.28 ± 56.55** (no Ln), **210.45 ± 27.53** (Er), **3.25–4.45** (La–Nd). **pedE:pedH ratio**: ~**6** (no Ln), ~**2** (Er), shifted toward **pedH** with La/Nd/mix; **pedH increased 1.9–4.2×**, and RT-qPCR showed **2.4-fold** pedH increase with La. (pqac-00000008, pqac-00000035) | Gorniak 2024 *mSphere* | https://doi.org/10.1128/msphere.00685-24 |
| 2024 update: cell-associated lanthanides | Single-cell ICP-MS after 1 µM exposure measured **0.058 ± 0.055 fg La/cell**, **0.125 ± 0.086 fg Nd/cell**, **0.152 ± 0.106 fg Er/cell**, corresponding to about **0.0025%–0.0068%** wet weight. Heavy-Ln effects were interpreted as possible **mismetallation** and altered sensing/signaling. (pqac-00000011, pqac-00000037) | Gorniak 2024 *mSphere* | https://doi.org/10.1128/msphere.00685-24 |
| Structural/sequence inference | PedH contains an **active-site Asp** (vs Ser in Ca²⁺-dependent PedE), a hallmark associated with **Ln³⁺ coordination** in XoxF/ExaF/PedH-type quinoprotein dehydrogenases. (pqac-00000007, pqac-00000026) | Wehrmann 2017 *mBio* | https://doi.org/10.1128/mbio.00570-17 |
| Application relevance | PedH-like Ln-dependent PQQ-ADHs are discussed as candidates for **biocatalysts**, **biosensors**, and for microbial **biomining/bioleaching/recycling** of rare earth elements. Broader studies indicate Ln-dependent PQQ-DHs are widespread: **6,886** PQQ-DH proteins detected in ocean metagenomes, **56%** with the Ln-binding motif, and Ln-dependent genes in **~20%** of resolved genomes. (pqac-00000031, pqac-00000027, pqac-00000033) | Wehrmann 2017 *mBio*; Voutsinos 2025 *ISME J.*; Skovran 2019 *Curr. Issues Mol. Biol.* | https://doi.org/10.1128/mbio.00570-17; https://doi.org/10.1101/2023.07.25.550467; https://doi.org/10.21775/cimb.033.101 |


*Table: This table condenses the key functional, biochemical, regulatory, and recent 2024 findings for PedH (PP_2679/Q88JH0) in Pseudomonas putida KT2440. It is designed as a data-rich reference linking each major claim to specific primary sources and URLs/DOIs.*