GO:0018685 alkane 1-monooxygenase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0018685 (alkane 1-monooxygenase activity) catalyzes the terminal hydroxylation of alkanes to 1-alkanols using a diiron active site and reduced rubredoxin as the electron donor.
• AlkB from Pseudomonas putida GPo1 is the paradigm enzyme for this activity, and its structure reveals a unique diiron center that activates dioxygen for C-H bond hydroxylation.
• The alkB gene is upregulated during colonization of plant leaves by Pseudomonas sp. FF2, linking this activity to environmental adaptation and host-microbe interactions.
• Engineering of membrane-bound AlkB from Marinobacter sp. has improved ω-hydroxylation of linear and branched aliphatic esters, demonstrating biotechnological potential.
• Alkane 1-monooxygenase activity is distinct from cytochrome P450-mediated ω-hydroxylation (e.g., CYP4A/20-HETE), though both can act on fatty acids and alkanes [3,5,6,7,8].
• CRISPR-based knockout, knock-in, and overexpression models enable causal dissection of alkB and related genes in alkane metabolism and host colonization [1,4].
Description
Alkane 1-monooxygenase activity (GO:0018685) is a molecular function that enables the terminal hydroxylation of alkanes to their corresponding 1-alkanols, using reduced rubredoxin as the electron donor and dioxygen as the oxidant. This activity is best characterized in the AlkB enzyme from Pseudomonas putida GPo1, a membrane-bound diiron monooxygenase that initiates the degradation of alkanes in many bacteria. The reaction is chemically challenging because it requires activation of a strong C-H bond under ambient conditions, a feat achieved by a non-heme diiron center that forms a high-valent iron-oxo intermediate. Beyond its role in microbial alkane catabolism, this activity has attracted attention for biotechnological applications such as selective ω-hydroxylation of aliphatic esters and for understanding bacterial colonization of plant surfaces [1,4]. Researchers study GO:0018685 to decipher mechanisms of C-H activation, to engineer enzymes for industrial biocatalysis, and to explore the ecological roles of alkane-degrading microbes [2,4]. The alkB gene is upregulated during colonization of Arabidopsis thaliana leaves by Pseudomonas sp. FF2, suggesting a role in plant-microbe interactions. This article provides a comprehensive overview of the definition, mechanism, key genes, disease relevance, and research methods for GO:0018685, with a focus on CRISPR-based models for functional studies.
alkane 1-monooxygenase activity At A Glance
| GO ID | GO:0018685 |
|---|---|
| GO term | alkane 1-monooxygenase activity |
| Ontology | molecular_function |
| Synonym | 1-hydroxylase activity; alkane 1-hydroxylase activity; alkane hydroxylase activity; alkane monooxygenase activity; alkane,reduced-rubredoxin:oxygen 1-oxidoreductase activity |
| Definition | Catalysis of the reaction: octane + reduced rubredoxin + O2 = 1-octanol + oxidized rubredoxin + H2O. |
| Major function | Terminal hydroxylation of alkanes to 1-alkanols, initiating alkane degradation |
| Cofactor | Diiron center; rubredoxin as electron donor |
| Localization | Membrane-bound in bacteria (e.g., Pseudomonas putida GPo1) |
| Representative enzyme | AlkB (alkane 1-monooxygenase) from Pseudomonas putida GPo1 |
What Is GO:0018685?
According to the Gene Ontology, GO:0018685 (alkane 1-monooxygenase activity) is defined as the catalysis of the reaction: octane + reduced rubredoxin + O2 = 1-octanol + oxidized rubredoxin + H2O. In other words, it is the enzyme activity that introduces a hydroxyl group at the terminal carbon of an alkane, converting it to a primary alcohol, while consuming molecular oxygen and reducing equivalents from rubredoxin. This activity is synonymous with alkane 1-hydroxylase, alkane hydroxylase, and alkane monooxygenase activity. The reaction is a key first step in the microbial degradation of alkanes, allowing organisms to use alkanes as a carbon and energy source.
Why Is alkane 1-monooxygenase activity Important in Cell Biology?
GO:0018685 is important because it represents a fundamental biological strategy for activating inert C-H bonds in alkanes, a reaction that is chemically difficult but essential for microbial utilization of hydrocarbons. This activity underpins the biodegradation of alkanes in the environment, including oil spills, and is a key determinant of bacterial colonization of hydrophobic surfaces such as plant leaves. Understanding its mechanism informs the design of biocatalysts for selective hydroxylation, which has applications in producing fine chemicals and pharmaceuticals. Moreover, the enzyme's diiron center serves as a model for non-heme iron monooxygenases, providing insights into oxygen activation and substrate specificity. From a biomedical perspective, although GO:0018685 is not directly linked to human disease, the broader family of cytochrome P450 ω-hydroxylases (e.g., CYP4A) that produce 20-HETE are involved in hypertension and cardiovascular disease, highlighting the importance of understanding alkane/fatty acid hydroxylation in physiology [3,5,6,7,8]. Thus, research on GO:0018685 contributes to both environmental microbiology and translational medicine.
• Enables microbial degradation of alkanes, a key process in bioremediation of oil-contaminated environments.
• Initiates the terminal hydroxylation of alkanes to 1-alkanols, which can be further oxidized to fatty acids.
• Supports bacterial colonization of plant leaves, as shown for Pseudomonas sp. FF2 alkB upregulation.
• Provides a paradigm for non-heme diiron monooxygenases that activate dioxygen for C-H bond functionalization.
• Offers biotechnological potential for selective ω-hydroxylation of aliphatic esters, useful in chemical synthesis.
• Contrasts with cytochrome P450 ω-hydroxylases (e.g., CYP4A) that produce 20-HETE, a mediator of hypertension and fibrosis [3,5,6,7,8].
• Serves as a target for enzyme engineering to improve activity and substrate range.
• Facilitates studies of host-microbe interactions through alkane metabolism on plant surfaces.
• Contributes to understanding of membrane-bound enzyme catalysis and electron transfer from rubredoxin.
• Enables the development of CRISPR models to dissect gene function in alkane metabolism [1,4].
What Happens During alkane 1-monooxygenase activity?
Substrate Binding and Electron Transfer
In simple terms: The enzyme grabs an alkane molecule and receives electrons from a partner protein.
Alkane 1-monooxygenase (AlkB) is a membrane-bound enzyme that binds its alkane substrate within a hydrophobic channel near the diiron active site. The enzyme requires reduced rubredoxin as an electron donor, which transfers electrons to the diiron center, priming it for oxygen activation. In Pseudomonas putida GPo1, the alkB gene product forms a complex with rubredoxin and rubredoxin reductase to shuttle electrons from NADH to the diiron center.
Dioxygen Activation and C-H Hydroxylation
In simple terms: Oxygen is split, and one oxygen atom is inserted into the alkane to make an alcohol.
The reduced diiron center reacts with molecular oxygen to form a high-valent iron-oxo species, which abstracts a hydrogen atom from the terminal carbon of the alkane, leading to hydroxylation and formation of a 1-alkanol. This mechanism is supported by structural and spectroscopic studies of AlkB, which reveal a unique diiron center coordinated by histidine and carboxylate residues. The reaction is highly regiospecific for the terminal carbon, producing 1-alkanols rather than subterminal alcohols.
Product Release and Further Metabolism
In simple terms: The alcohol product is released and can be further processed by other enzymes.
After hydroxylation, the 1-alkanol product is released from the active site and can be further oxidized by alcohol dehydrogenases and aldehyde dehydrogenases to a fatty acid, which enters beta-oxidation. This pathway allows bacteria to use alkanes as a sole carbon and energy source. In some organisms, the alkane 1-monooxygenase activity is part of a larger alkane degradation operon, including rubredoxin and rubredoxin reductase.
Regulation and Environmental Role
In simple terms: The gene for this enzyme can be turned on when needed, such as during plant colonization.
The expression of alkB is regulated in response to environmental cues; for example, in Pseudomonas sp. FF2, alkB is upregulated during colonization of Arabidopsis thaliana leaves, suggesting a role in adapting to the leaf surface. This regulation may involve two-component systems or other transcriptional regulators that sense alkanes or plant-derived signals. The ability to degrade alkanes may provide a competitive advantage in the phyllosphere.
Key Genes Involved in GO:0018685 alkane 1-monooxygenase activity
The following genes and proteins are directly or functionally associated with alkane 1-monooxygenase activity (GO:0018685) and its broader context.
| Gene | Major Role | Research Relevance |
|---|---|---|
| alkB (Pseudomonas putida GPo1) | Alkane 1-monooxygenase; terminal hydroxylation of alkanes | Paradigm enzyme for GO:0018685; structural and mechanistic studies |
| alkB (Pseudomonas sp. FF2) | Alkane 1-monooxygenase; upregulated during leaf colonization | Host-microbe interaction; plant colonization |
| alkB (Marinobacter sp.) | Membrane-bound alkane monooxygenase; ω-hydroxylation of esters | Enzyme engineering for improved activity |
| rubA (rubredoxin) | Electron transfer to AlkB | Essential for catalytic turnover |
| rubB (rubredoxin reductase) | Reduces rubredoxin using NADH | Electron transport chain for AlkB |
| CYP4A (human) | Cytochrome P450 ω-hydroxylase; produces 20-HETE | Related activity in fatty acid hydroxylation; hypertension [3,5,6,7,8] |
| CYP4F2 (human) | ω-hydroxylase; 20-HETE synthesis | Hypertension and cardiovascular disease [3,5] |
| GPR75 (human) | Receptor for 20-HETE | Mediates 20-HETE effects in hypertension |
| ALKBH1 (human) | AlkB homolog; DNA/RNA demethylase | Not directly GO:0018685 but shares AlkB family name; distinct function |
| ALKBH2 (human) | AlkB homolog; DNA repair demethylase | Distinct from GO:0018685; relevant to cancer biology |
| ALKBH3 (human) | AlkB homolog; RNA/DNA demethylase | Distinct from GO:0018685; cancer and RNA biology |
| alkM (Acinetobacter) | Alkane monooxygenase | Alternative enzyme for alkane degradation |
| ladA (Geobacillus) | Alkane monooxygenase | Thermophilic alkane degradation |
| alkane monooxygenase (Rhodococcus) | Alkane hydroxylation | Bioremediation and biocatalysis |
| CYP153 (various bacteria) | Cytochrome P450 alkane hydroxylase | Alternative alkane hydroxylation system |
| alkB (Pseudomonas aeruginosa) | Alkane degradation | Pathogen physiology and biofilm formation |
| alkB (Alcanivorax borkumensis) | Alkane degradation | Oil spill bioremediation |
| alkB (Mycobacterium tuberculosis) | Alkane hydroxylation | Potential role in host lipid metabolism |
How Is alkane 1-monooxygenase activity Regulated?
The expression and activity of alkane 1-monooxygenase (AlkB) are regulated at multiple levels. In Pseudomonas putida GPo1, the alkBFGHJKL operon is induced by alkanes and repressed by glucose via catabolite repression. The alkS gene encodes a transcriptional regulator that activates the alkBFGHJKL promoter in the presence of alkanes. In Pseudomonas sp. FF2, alkB is upregulated during colonization of Arabidopsis thaliana leaves, indicating regulation by plant-derived signals or environmental conditions. Additionally, the activity of AlkB depends on the availability of reduced rubredoxin, which is regenerated by rubredoxin reductase using NADH. Thus, both transcriptional and post-translational mechanisms control GO:0018685 activity.
alkane 1-monooxygenase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| CYP4A | Hypertension, cardiac hypertrophy, fibrosis | CYP4A knockout or overexpression in H9c2 cells or mouse models [3,5,7] |
| CYP4F2 | Hypertension, cardiovascular disease | CYP4F2 knockout mice or human cell lines [3,5] |
| GPR75 | Hypertension, vascular remodeling | GPR75 knockout or knock-in models |
| alkB (Pseudomonas sp. FF2) | Plant colonization, host-microbe interaction | alkB knockout in Pseudomonas sp. FF2; Arabidopsis infection model |
| alkB (Marinobacter sp.) | Biocatalysis, ω-hydroxylation of esters | Engineered alkB overexpression in E. coli or Pseudomonas |
Alkane 1-Monooxygenase and Host-Microbe Interactions
Although GO:0018685 is not directly linked to human disease, the ability of bacteria to degrade alkanes can influence host-microbe interactions. For instance, Pseudomonas sp. FF2 upregulates alkB during colonization of Arabidopsis thaliana leaves, suggesting a role in plant colonization that could affect plant health. In humans, bacterial alkane metabolism in the gut or on skin might influence microbiome composition, but direct evidence is lacking. The broader family of cytochrome P450 ω-hydroxylases, such as CYP4A and CYP4F2, produce 20-HETE, which is implicated in hypertension, cardiac hypertrophy, and fibrosis [3,5,6,7,8]. These enzymes share the ability to hydroxylate fatty acids but are structurally distinct from AlkB [2,3].
20-HETE and Cardiovascular Disease
The CYP4A/20-HETE/GPR75 axis is a major contributor to hypertension and target-organ damage. 20-HETE, produced by CYP4A and CYP4F2, acts as a vasoconstrictor and promotes neovascularization, cardiac hypertrophy, and fibrosis [3,5,6,7,8]. Studies in H9c2 cells show that 20-HETE mediates angiotensin II-induced cardiac hypertrophy via ROS and Ca2+ signaling. Arachidonic acid intake can promote hypertension through CYP4A-mediated 20-HETE overproduction. While these enzymes are not alkane 1-monooxygenases, they highlight the physiological importance of terminal hydroxylation reactions in human disease [3,5,6,7,8].
From alkane 1-monooxygenase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does alkB contribute to plant leaf colonization? | alkB knockout in Pseudomonas sp. FF2; Arabidopsis thaliana infection |
| What is the catalytic mechanism of AlkB? | Site-directed mutagenesis of diiron ligands; X-ray crystallography |
| Can AlkB be engineered for improved ω-hydroxylation? | Directed evolution or rational design of Marinobacter sp. AlkB; overexpression in E. coli |
| Is CYP4A causally involved in hypertension? | CYP4A knockout or transgenic mice; 20-HETE measurements [3,5,7] |
| Does GPR75 mediate 20-HETE effects? | GPR75 knockout mice or cells; vascular reactivity assays |
| What is the role of alkB in alkane degradation? | alkB knockout in Pseudomonas putida GPo1; growth on alkanes |
How to Study the alkane 1-monooxygenase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| GC-MS | Alkane consumption and 1-alkanol production | Enzyme activity assays |
| RNA-seq | Transcript levels of alkB and related genes | Gene expression during colonization or alkane exposure |
| qRT-PCR | Relative expression of alkB | Validation of RNA-seq data |
| X-ray crystallography | Three-dimensional structure of AlkB | Mechanistic studies of diiron center |
| Mössbauer spectroscopy | Electronic structure of diiron center | Characterization of iron oxidation states |
| Site-directed mutagenesis | Role of specific residues in catalysis | Identification of catalytic and substrate-binding residues |
| Directed evolution | Improved enzyme activity or substrate range | Engineering of Marinobacter sp. AlkB |
| CRISPR-Cas9 knockout | Loss-of-function phenotype | Testing gene essentiality in alkane metabolism |
Enzymatic Assays for Alkane 1-Monooxygenase Activity
Alkane 1-monooxygenase activity can be measured using whole-cell or membrane fractions with alkanes as substrates, monitoring the formation of 1-alkanols by gas chromatography or mass spectrometry. The reaction requires reduced rubredoxin or a suitable electron donor system, such as NADH and rubredoxin reductase. For engineered enzymes, activity can be assessed using aliphatic esters as substrates and detecting ω-hydroxylated products.
Gene Expression Analysis (RNA-seq, qRT-PCR)
Transcript levels of alkB and associated genes can be quantified by RNA-seq or qRT-PCR under different conditions, such as during plant colonization or exposure to alkanes. In Pseudomonas sp. FF2, alkB upregulation during Arabidopsis leaf colonization was demonstrated using RNA-seq. Such methods help identify regulatory pathways controlling GO:0018685.
Structural and Spectroscopic Methods
X-ray crystallography and cryo-electron microscopy can determine the structure of AlkB and its diiron center. Spectroscopic techniques such as Mössbauer, EPR, and resonance Raman spectroscopy provide insights into the electronic structure of the diiron center and reaction intermediates. These methods are essential for understanding the catalytic mechanism of GO:0018685.
CRISPR-Based Functional Genomics
CRISPR-Cas9 knockout, knock-in, and overexpression models enable causal testing of genes involved in alkane metabolism [1,4]. For example, knocking out alkB in Pseudomonas sp. FF2 can reveal its role in leaf colonization. Overexpression of engineered alkB in heterologous hosts can improve ω-hydroxylation activity. These approaches are powerful for dissecting the function of GO:0018685 in complex biological systems.
How CRISPR Can Be Used to Study GO:0018685 alkane 1-monooxygenase activity
Knockout
CRISPR-Cas9 knockout of alkB in Pseudomonas sp. FF2 or Pseudomonas putida GPo1 can abolish alkane 1-monooxygenase activity, leading to loss of growth on alkanes and reduced plant colonization [1,2]. Such knockouts are valuable for confirming the role of alkB in these processes and for identifying compensatory pathways.
Point Mutation
Point mutations in the diiron center of AlkB (e.g., substituting histidine or carboxylate ligands) can be introduced using CRISPR-Cas9 homology-directed repair to dissect the catalytic mechanism. These mutants help determine the roles of specific residues in oxygen activation and substrate hydroxylation.
Knock-in
Knock-in of tagged alkB (e.g., FLAG or GFP) at the endogenous locus allows visualization and purification of the enzyme for interaction studies. Knock-in of engineered alkB variants can also be used to test improved activity in the native host.
Overexpression
CRISPR activation (CRISPRa) or plasmid-based overexpression of alkB can increase alkane 1-monooxygenase activity, enabling enhanced alkane degradation or biotransformation. Overexpression in heterologous hosts such as E. coli is commonly used for enzyme production and engineering.
How EDITGENE Supports alkane 1-monooxygenase activity Research
Researchers studying alkane 1-monooxygenase activity-related genes often need to determine whether a candidate gene is causally involved in alkane metabolism, host colonization, or related physiological processes. EDITGENE provides comprehensive CRISPR-based services to generate knockout, point-mutation, knock-in, and overexpression cell models, as well as CRISPR library screening and bioinformatics support, enabling rigorous functional studies of GO:0018685 and its associated genes.
Contact EDITGENE today to design your custom CRISPR model for alkane 1-monooxygenase activity research.
Frequently Asked Questions About alkane 1-monooxygenase activity
What is alkane 1-monooxygenase activity?
Alkane 1-monooxygenase activity (GO:0018685) is the catalysis of the terminal hydroxylation of alkanes to 1-alkanols, using reduced rubredoxin and O2, as defined by the Gene Ontology.
What genes are involved in alkane 1-monooxygenase activity?
The primary gene is alkB, encoding the enzyme AlkB, along with rubA (rubredoxin) and rubB (rubredoxin reductase) for electron transfer. Homologs exist in Pseudomonas, Marinobacter, and other bacteria [1,4].
What is the reaction catalyzed by alkane 1-monooxygenase?
The reaction is: octane + reduced rubredoxin + O2 = 1-octanol + oxidized rubredoxin + H2O, representing terminal hydroxylation of an alkane.
How is alkane 1-monooxygenase activity regulated?
It is regulated transcriptionally by alkane-responsive regulators and catabolite repression, and post-translationally by electron donor availability. In Pseudomonas sp. FF2, alkB is upregulated during plant colonization.
What is the difference between alkane 1-monooxygenase and cytochrome P450?
Alkane 1-monooxygenase (AlkB) is a non-heme diiron enzyme that uses rubredoxin, while cytochrome P450 enzymes (e.g., CYP4A) are heme-containing and use NADPH via P450 reductase, though both can hydroxylate fatty acids [2,3].
Is alkane 1-monooxygenase involved in human disease?
No direct link to human disease is established for GO:0018685, but related cytochrome P450 ω-hydroxylases (CYP4A/CYP4F2) produce 20-HETE, which is implicated in hypertension and cardiovascular disease [3,5,6,7,8].
How can I study alkane 1-monooxygenase activity in the lab?
You can use enzymatic assays with GC-MS, RNA-seq for gene expression, structural methods like X-ray crystallography, and CRISPR-based knockouts or overexpression models [1,2,4].
What are the substrates of alkane 1-monooxygenase?
Alkanes such as octane are typical substrates, but the enzyme can also act on aliphatic esters for ω-hydroxylation, as shown for engineered Marinobacter sp. AlkB [2,4].
What is the role of rubredoxin in alkane 1-monooxygenase activity?
Rubredoxin is the physiological electron donor that transfers electrons from rubredoxin reductase to the diiron center of AlkB, enabling oxygen activation.
Can alkane 1-monooxygenase be used in biotechnology?
Yes, engineered AlkB variants have improved ω-hydroxylation of aliphatic esters, making them attractive for biocatalysis and chemical synthesis.
Conclusion
Alkane 1-monooxygenase activity (GO:0018685) is a fascinating molecular function that enables the terminal hydroxylation of alkanes, a key step in microbial alkane degradation and a model for non-heme diiron chemistry. Its representative enzyme, AlkB, is structurally and mechanistically well-characterized, and its gene is upregulated during plant colonization, linking it to ecological interactions. While not directly implicated in human disease, related cytochrome P450 ω-hydroxylases play critical roles in hypertension and cardiovascular pathology [3,5,6,7,8]. Advances in enzyme engineering and CRISPR-based models continue to expand our understanding and application of this activity [1,4]. EDITGENE offers comprehensive CRISPR services to support functional studies of alkB and related genes, empowering researchers to explore the biology and biotechnology of GO:0018685.
References
- 1. Schlechter R et al.. 2025. The Alkane 1-Monooxygenase Gene alkB of Pseudomonas sp. FF2 Is Upregulated During Colonisation of Arabidopsis thaliana Leaves.. Environ Microbiol Rep 17(6):e70242 PMID: 41287462
- 2. Groves JT et al.. 2023. Structure and Function of Alkane Monooxygenase (AlkB).. Acc Chem Res 56(24):3665-3675 PMID: 38032826
- 3. Froogh G et al.. 2022. The CYP/20-HETE/GPR75 axis in hypertension.. Adv Pharmacol 94:1-25 PMID: 35659370
- 4. Spasic J et al.. 2026. Engineering membrane-bound alkane monooxygenase from Marinobacter sp. for increased activity in the selective ω-hy-droxylation of linear and branched aliphatic esters.. Protein Sci 35(4):e70511 PMID: 41841755
- 5. Zhou Z et al.. 2026. Arachidonic acid intake promotes hypertension and target-organ fibrosis through CYP4A-mediated 20-HETE overproduction: Integrated evidence from human and animal studies.. Clin Exp Hypertens 48(1):2611130 PMID: 41491652
- 6. Chen L et al.. 2012. 20-HETE in neovascularization.. Prostaglandins Other Lipid Mediat 98(3-4):63-8 PMID: 22227460
- 7. Han J et al.. 2025. 20-HETE mediates Ang II-induced cardiac hypertrophy via ROS and Ca(2+) signaling in H9c2 cells.. Sci Rep 15(1):2342 PMID: 39825084
- 8. Fleming I. 2001. Cytochrome p450 and vascular homeostasis.. Circ Res 89(9):753-62 PMID: 11679404
