GO:0036185 13-lipoxin reductase activity: Mechanism

GO:0036185, 13-lipoxin reductase activity, is a molecular_function term in the Gene Ontology that describes a specific NADH-dependent oxidoreductase reaction. The term captures the conversion of 15-oxo-(5S,6R)-dihydroxy-(7E,9E,11Z,13E)-eicosatetraenoate to 15-oxo-(5S,6R)-dihydroxy-(7E,9E,11Z)-eicosatrienoate, with concomitant oxidation of NADH to NAD+. This reaction sits within the broader lipoxin and oxoeicosanoid metabolic network, which is central to the resolution of inflammation and to the control of innate immune cell trafficking. For researchers, GO:0036185 matters because it provides a precise, computable definition that can be used to annotate enzyme candidates, interpret lipidomic datasets, and design functional assays. The term is also a useful anchor for comparative genomics and for pathway enrichment analyses in inflammation and redox biology. Because the reaction consumes NADH, it directly interfaces with cellular energy metabolism and oxidative stress responses. Despite its clear biochemical definition, the human gene or genes responsible for 13-lipoxin reductase activity remain incompletely resolved. This gap makes GO:0036185 an attractive target for CRISPR-based functional genomics, where candidate oxidoreductases can be knocked out, point-mutated, or overexpressed to test causality. The sections below summarize the definition, mechanism, candidate genes, disease links, and experimental models relevant to this term.

13-lipoxin reductase activity (GO:0036185) is defined as the catalysis of the reaction: 15-oxo-(5S,6R)-dihydroxy-(7E,9E,11Z,13E)-eicosatetraenoate + NADH + H+ = 15-oxo-(5S,6R)-dihydroxy-(7E,9E,11Z)-eicosatrienoate + NAD+. In other words, it is an NADH-dependent reduction that saturates a specific double bond in an oxo-lipoxin intermediate, converting an eicosatetraenoate to an eicosatrienoate. The term is a molecular_function annotation and does not by itself specify a gene, a cellular location, or a biological process.

GO:0036185 is important because it defines a specific enzymatic step in the lipoxin/oxoeicosanoid metabolic axis, a pathway that actively terminates inflammation and promotes tissue repair. The reaction consumes NADH, so its activity is coupled to the cellular redox state and to NAD+ regeneration, which influences energy metabolism and oxidative stress responses. Precise annotation of this activity enables researchers to interpret lipidomic and transcriptomic datasets, to prioritize candidate genes for functional testing, and to design CRISPR models that establish causality.

The following genes and protein families are candidate or associated enzymes that may carry 13-lipoxin reductase activity or regulate its substrate supply.

13-lipoxin reductase activity is regulated at multiple levels. Substrate availability depends on upstream lipoxygenase and dehydrogenase reactions that generate oxo-lipoxin intermediates. Enzyme expression can be influenced by redox-sensitive transcription factors such as NFE2L2 (Nrf2), which coordinates antioxidant and metabolic gene programs. The NADH/NAD+ ratio, which shifts with exercise, metabolic stress, and mitochondrial function, can also modulate flux through NADH-dependent reductases. Post-translational modifications and subcellular localization further tune activity.

Dysregulated lipoxin and oxoeicosanoid metabolism is associated with chronic inflammatory diseases, including asthma, arthritis, and inflammatory bowel disease. Because 13-lipoxin reductase activity participates in the conversion of oxo-lipoxin intermediates, altered activity could shift the balance between pro-resolving and pro-inflammatory lipid mediators. Functional studies using CRISPR models are needed to test whether candidate genes carrying this activity modify inflammatory outcomes.

NADH-dependent reductases are sensitive to cellular redox state, which is perturbed in heart failure, obesity, and diabetes. Changes in 13-lipoxin reductase activity could therefore influence lipid mediator profiles in cardiovascular and metabolic disease. Exercise and metabolic interventions that alter NADH/NAD+ balance may indirectly affect this activity.

Eicosanoid-metabolizing enzymes, including aldo-keto reductases and prostaglandin reductases, are implicated in cancer progression and in the tumor immune microenvironment. If 13-lipoxin reductase activity contributes to the local lipid mediator pool, its dysregulation could affect immune cell recruitment and tumor inflammation. CRISPR knockout and overexpression models can help establish causal links.

Targeted liquid chromatography-tandem mass spectrometry (LC-MS/MS) can quantify the substrate and product of 13-lipoxin reductase activity in cell lysates or media. Stable isotope-labeled internal standards improve quantification and allow comparison across CRISPR knockout and wild-type cells. This approach directly measures flux through GO:0036185.

Purified recombinant candidate enzymes can be incubated with the oxo-lipoxin substrate and NADH, and product formation monitored spectrophotometrically or by LC-MS/MS. These assays define kinetic parameters and confirm that a gene product carries 13-lipoxin reductase activity. Point-mutant proteins can be tested in parallel to map catalytic residues.

Pooled CRISPR knockout libraries can be screened for changes in oxo-lipoxin reduction using lipidomic or reporter-based readouts. Hit genes can then be validated individually with clonal knockout lines. This workflow connects genotype to enzymatic activity at scale.

RNA-seq of CRISPR models and disease samples can reveal co-expression networks linking candidate genes to lipoxin and oxoeicosanoid pathways. Pathway enrichment using GO:0036185 annotations helps interpret these datasets. Integrating transcriptomics with lipidomics provides a multi-omic view of the activity.

Researchers studying 13-lipoxin reductase activity-related genes often need to determine whether a candidate gene is causally involved in the reaction, which residues are required for catalysis, and how the activity changes in disease models. EDITGENE provides the CRISPR cell model and screening services needed to answer these questions with rigor and reproducibility.

GO:0036185, 13-lipoxin reductase activity, defines a specific NADH-dependent reduction step in oxo-lipoxin metabolism that connects eicosanoid biology to cellular redox state. Although the responsible human gene or genes remain incompletely resolved, the term provides a precise annotation for lipidomic, transcriptomic, and functional genomics studies. CRISPR-based knockout, point-mutation, knock-in, and overexpression models are essential tools for establishing causality and for translating this activity into disease-relevant insights. Researchers interested in inflammation resolution, cardiovascular biology, and metabolic stress will benefit from integrating GO:0036185 into their experimental and bioinformatic workflows. EDITGENE offers the cell model and screening services needed to accelerate this work.