GO:0016639 oxidoreductase activity, acting on the CH-NH2 group of donors, NAD or NADP as acceptor: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0016639 describes a molecular function: catalysis of a redox reaction in which a CH-NH2 group donates electrons and NAD+ or NADP is reduced [1,2].
• This activity is central to mitochondrial NADPH generation, proline biosynthesis, and lipoylation-dependent oxidative metabolism [1,2].
• NAD kinase (NADK) supplies the NADP(H) pool that feeds CH-NH2 oxidoreductases, and its regulation is critical in cancer and folate metabolism [3,4,6,8].
• Loss of this activity impairs mitochondrial fatty acid synthesis and lipoylation, linking it to metabolic disease.
• Cryo-EM structures of human NADK reveal regulatory mechanisms that control NADP(H) availability for this oxidoreductase class.
• CRISPR knockout, point-mutation, and knock-in models are essential to dissect the causal roles of these enzymes in disease [1,2,6].
Description
GO:0016639, oxidoreductase activity, acting on the CH-NH2 group of donors, NAD or NADP as acceptor, is a molecular function term in the Gene Ontology that defines a specific class of redox enzymes. These enzymes catalyze the oxidation of a CH-NH2 group, using NAD+ or NADP as the electron acceptor, thereby generating NADH or NADPH [1,2]. This activity is fundamental to cellular metabolism because it connects amino acid and amine oxidation to the regeneration of reducing equivalents, particularly in mitochondria and chloroplasts [1,2,5]. Researchers study this term to understand how cells maintain redox balance, synthesize proline, and support lipoylation-dependent oxidative metabolism [1,2]. The activity is also linked to NADP(H) homeostasis, which is controlled by NAD kinase and NADP(H) phosphatases [3,4,7]. Because NADPH is a key reducing agent for biosynthesis and antioxidant defense, dysregulation of GO:0016639-related enzymes has broad implications for cancer, metabolic disorders, and plant stress responses [6,7,8].
oxidoreductase activity, acting on the CH-NH2 group of donors, NAD or NADP as acceptor At A Glance
| GO ID | GO:0016639 |
|---|---|
| GO term | oxidoreductase activity, acting on the CH-NH2 group of donors, NAD or NADP as acceptor |
| Ontology | molecular_function |
| Synonym | None listed in QuickGO |
| Major function | Catalyzes oxidation of a CH-NH2 group using NAD+ or NADP as electron acceptor |
| Cofactor | NAD+ or NADP |
| Substrate class | CH-NH2 group donors (e.g., amino acids, amines) |
| Reaction direction | Oxidation of donor; reduction of NAD(P)+ to NAD(P)H |
| Related activities | NAD kinase, NADP(H) phosphatase, proline biosynthesis enzymes |
What Is GO:0016639?
In simple terms, GO:0016639 describes enzymes that remove hydrogen from a CH-NH2 group and transfer it to NAD+ or NADP, reducing the cofactor to NADH or NADPH. The QuickGO definition states: Catalysis of an oxidation-reduction (redox) reaction in which a CH-NH2 group acts as a hydrogen or electron donor and reduces NAD+ or NADP. This activity is a subset of oxidoreductases acting on CH-NH2 donors, distinguished by its strict use of NAD+ or NADP as the acceptor. It does not include enzymes that use other acceptors such as oxygen or quinones. The term is a molecular_function in the Gene Ontology and has no synonyms listed in QuickGO.
Why Is oxidoreductase activity, acting on the CH-NH2 group of donors, NAD or NADP as acceptor Important in Cell Biology?
GO:0016639 is important because it defines a core redox function that sustains mitochondrial NADPH pools, proline biosynthesis, and lipoylation-dependent oxidative metabolism [1,2]. These processes are essential for cell survival under metabolic stress and for biosynthetic pathways that require reducing power [1,2]. Dysregulation of this activity contributes to cancer cell proliferation, metabolic disorders, and impaired folate-dependent nucleotide synthesis [6,8]. In plants, related NADP(H) balance mechanisms regulate chloroplast function and stress responses. Thus, understanding GO:0016639 helps researchers identify therapeutic targets and interpret metabolic phenotypes.
• Supports mitochondrial NADPH generation for proline biosynthesis.
• Fuels mitochondrial fatty acid synthesis and lipoylation for oxidative metabolism.
• Connects to NADP(H) homeostasis via NAD kinase and NADP(H) phosphatases [3,4,7].
• Is conditionally essential for folate-dependent nucleotide synthesis in cancer cells.
• Represents a therapeutic target in cancer due to NAD+ kinase dependency.
• Plays a role in photosynthetic light reactions and chloroplast redox balance [5,7].
• Can be studied with CRISPR knockout to reveal metabolic vulnerabilities [1,2,6].
• Involves enzymes that are structurally and mechanistically diverse but share cofactor specificity.
• Links amino acid metabolism to redox signaling and antioxidant defense [1,2].
• Provides a framework for understanding inherited metabolic disorders of NAD(P) metabolism [3,4].
Molecular Mechanism of oxidoreductase activity, acting on the CH-NH2 group of donors, NAD or NADP as acceptor
Substrate recognition and CH-NH2 group activation
In simple terms: The enzyme grabs a molecule that has a CH-NH2 group and prepares it for oxidation.
Enzymes with GO:0016639 activity bind substrates containing a CH-NH2 group, such as amino acids or amines, and position them for hydride transfer. The CH-NH2 group acts as the hydrogen donor, meaning the enzyme abstracts a hydride equivalent from the carbon-nitrogen bond region [1,2]. This step is often coupled to cofactor binding, ensuring that NAD+ or NADP is properly oriented for catalysis. Structural studies of related NADP(H)-dependent enzymes show that substrate specificity is achieved through conserved active-site residues that interact with the amino group.
Hydride transfer to NAD+ or NADP
In simple terms: The enzyme moves a hydrogen from the substrate to NAD+ or NADP, turning it into NADH or NADPH.
The catalytic core of GO:0016639 enzymes facilitates hydride transfer from the CH-NH2 group to the nicotinamide ring of NAD+ or NADP. This reduction generates NADH or NADPH, which can then be used in biosynthetic or antioxidant pathways [1,2]. The reaction is stereospecific and often rate-limited by conformational changes that align the substrate and cofactor. In mitochondria, this activity contributes to the NADPH pool required for proline biosynthesis and lipoylation [1,2].
Cofactor regeneration and NADP(H) balance
In simple terms: The cell must keep enough NADP available for these enzymes to work, which is managed by other enzymes like NAD kinase.
NAD kinase (NADK) phosphorylates NAD+ to generate NADP+, the preferred cofactor for many GO:0016639 enzymes [3,4]. Human NADK is regulated by calcium/calmodulin and undergoes conformational changes that control its activity, as revealed by cryo-EM. Cytosolic NADK is conditionally essential for folate-dependent nucleotide synthesis, linking cofactor supply to one-carbon metabolism. In plants, a chloroplast-localized NADP(H) phosphatase, CCR4C, regulates NAD(P)(H) balance, affecting redox homeostasis.
Integration with mitochondrial metabolism
In simple terms: These enzymes work inside mitochondria to support fatty acid synthesis and energy production.
Mitochondrial NADPH generated by GO:0016639-related activities fuels mitochondrial fatty acid synthesis and lipoylation, which are required for oxidative metabolism. Loss of this NADPH supply impairs lipoylation of key enzymes such as pyruvate dehydrogenase, reducing oxidative capacity. This integration highlights how a single molecular function can influence whole-cell metabolic flux. Proline biosynthesis also depends on mitochondrial NADP(H) generation, further emphasizing the role of this activity in biosynthetic pathways.
Regulation by cellular redox state and signaling
In simple terms: The activity of these enzymes can be turned up or down based on the cell's redox balance and signals.
The activity of GO:0016639 enzymes is influenced by the availability of NAD+ and NADP+, which in turn reflects cellular redox state [3,4]. NADK activity is regulated by calcium/calmodulin and post-translational modifications, controlling NADP+ supply. In cancer, NAD+ kinase is a therapeutic target because rapidly proliferating cells have increased demand for NADPH. Folate metabolism also intersects with this regulation, as cytosolic NADK is conditionally essential for nucleotide synthesis.
Key Genes Involved in GO:0016639 oxidoreductase activity, acting on the CH-NH2 group of donors, NAD or NADP as acceptor
The following genes encode proteins that either possess GO:0016639 activity or directly regulate the NAD(P) cofactor pools required for this oxidoreductase class.
| Gene | Major Role | Research Relevance |
|---|---|---|
| NADK | Phosphorylates NAD+ to NADP+ | Regulates cofactor supply for GO:0016639 enzymes; target in cancer [3,4,8] |
| PYCR1 | Proline biosynthesis using NAD(P)H | Mitochondrial NADPH-dependent proline synthesis |
| PYCR2 | Proline biosynthesis | Related to PYCR1 in proline metabolism |
| ALDH18A1 | Glutamate to pyrroline-5-carboxylate | Upstream of proline biosynthesis |
| LIAS | Lipoylation of mitochondrial enzymes | Depends on NADPH from mitochondrial sources |
| LIPT1 | Lipoylation transfer | Linked to mitochondrial fatty acid synthesis |
| FASN | Fatty acid synthesis | Mitochondrial fatty acid synthesis uses NADPH |
| MTHFD2 | Folate-dependent one-carbon metabolism | Cytosolic NADK supports nucleotide synthesis |
| CCR4C | Chloroplast NADP(H) phosphatase | Regulates NAD(P)(H) balance in plants |
| NADK2 | Mitochondrial NAD kinase | Mitochondrial NADP(H) generation [1,2] |
| G6PD | Pentose phosphate pathway | Generates cytosolic NADPH, complementary to GO:0016639 |
| IDH2 | Mitochondrial NADPH production | Supports mitochondrial NADPH pool [1,2] |
| ME1 | Malic enzyme | Produces NADPH in cytosol |
| GLUD1 | Glutamate dehydrogenase | Uses NAD(P)+ as acceptor for CH-NH2 oxidation |
| MAOB | Monoamine oxidase B | Oxidizes amines using NAD+? Not NAD(P) acceptor; excluded from GO:0016639 |
| D2HGDH | D-2-hydroxyglutarate dehydrogenase | Uses NAD+ but substrate not CH-NH2; excluded |
| PRODH | Proline dehydrogenase | Uses NAD+ but substrate is CH-NH2? Proline is secondary amine; not CH-NH2 |
| P5CR | Pyrroline-5-carboxylate reductase | Uses NAD(P)H for proline synthesis |
How Is oxidoreductase activity, acting on the CH-NH2 group of donors, NAD or NADP as acceptor Regulated?
The activity of GO:0016639 enzymes is regulated at multiple levels. Cofactor availability is controlled by NAD kinase (NADK), which is activated by calcium/calmodulin and modulated by structural changes. Cytosolic NADK is conditionally essential for folate-dependent nucleotide synthesis, linking its regulation to one-carbon metabolism. In plants, CCR4C phosphatase regulates NAD(P)(H) balance in chloroplasts. Additionally, NAD+ kinase is a therapeutic target in cancer, where increased NADPH demand drives proliferation. These regulatory mechanisms ensure that CH-NH2 oxidoreductase activity matches cellular redox and biosynthetic needs.
oxidoreductase activity, acting on the CH-NH2 group of donors, NAD or NADP as acceptor and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| NADK | Cancer proliferation and NADPH supply | Knockout in cancer cell lines; point mutation of catalytic residues |
| NADK2 | Mitochondrial NADP(H) generation and proline biosynthesis | Knockout in HEK293T; rescue with NADPH |
| LIAS | Lipoylation defects and metabolic disease | Knockout in fibroblasts; lipoic acid supplementation |
| MTHFD2 | Folate-dependent nucleotide synthesis | Knockout in cancer cells; NADK conditional essentiality |
| CCR4C | Plant chloroplast redox balance | Arabidopsis knockout; stress phenotyping |
Cancer metabolism and NADPH dependency
Cancer cells often require elevated NADPH to support biosynthesis and antioxidant defense. NAD+ kinase, which supplies NADP+ for GO:0016639 enzymes, is a therapeutic target in cancer. Cytosolic NADK is conditionally essential for folate-dependent nucleotide synthesis, making it a potential vulnerability in tumors. Mitochondrial NADPH generation also supports proline biosynthesis, which can promote cancer cell survival.
Metabolic disorders and lipoylation defects
Mitochondrial NADPH fuels fatty acid synthesis and lipoylation; disruption of this pathway impairs oxidative metabolism. Defects in lipoylation are associated with severe metabolic disorders, and GO:0016639-related enzymes contribute to this process. Proline biosynthesis defects, linked to mitochondrial NADP(H) generation, can cause developmental and neurological abnormalities.
Plant stress responses and chloroplast redox
In plants, NADP(H) balance is critical for photosynthesis and stress tolerance. CCR4C, a chloroplast-localized NADP(H) phosphatase, regulates NAD(P)(H) balance and affects redox homeostasis. The light reactions of photosynthesis depend on NADP+ reduction, highlighting the importance of cofactor supply for GO:0016639-like activities.
From oxidoreductase activity, acting on the CH-NH2 group of donors, NAD or NADP as acceptor-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of NADK impair mitochondrial NADPH and proline synthesis? | NADK2 knockout cell line |
| Does mitochondrial NADPH fuel lipoylation? | LIAS or NADK2 knockout with lipoic acid rescue |
| Is cytosolic NADK essential for folate-dependent nucleotide synthesis? | Conditional NADK knockout in cancer cells |
| How does NADK structure regulate activity? | Point mutations in NADK based on cryo-EM structure |
| Does CCR4C regulate chloroplast NADP(H) balance? | Arabidopsis ccr4c knockout |
| Can NADK be targeted in cancer? | Overexpression of NADK in cancer cell lines; inhibitor testing |
How to Study the oxidoreductase activity, acting on the CH-NH2 group of donors, NAD or NADP as acceptor Process
| Method | What It Measures | Typical Application |
|---|---|---|
| LC-MS metabolomics | NADP+, NADPH, proline levels | Quantify impact of NADK knockout |
| Cryo-EM | Protein structure and conformational states | Design point mutations in NADK |
| RNA-seq | Transcriptional changes | Identify compensatory pathways in knockout cells |
| Proteomics | Protein abundance and lipoylation | Assess mitochondrial lipoylation defects |
| Genetically encoded sensors | Real-time NADPH dynamics | Monitor redox changes in live cells |
| CRISPR knockout | Gene function loss | Test essentiality of NADK in cancer |
| Rescue experiments | Specificity of phenotype | Add NADPH or proline to rescue |
| Plant phenotyping | Stress tolerance and chloroplast function | Analyze ccr4c mutants |
Genetic knockout and metabolic profiling
CRISPR knockout of NADK, NADK2, or PYCR1 followed by metabolomics can reveal how GO:0016639 activity affects NADPH pools and proline levels [1,2]. Targeted metabolomics using LC-MS quantifies NADP+, NADPH, and proline. Rescue experiments with NADPH or proline confirm specificity.
Structural biology and point mutations
Cryo-EM structures of human NADK provide a template for designing point mutations that disrupt catalysis or regulation. These mutants can be expressed in cells to test effects on NADP(H) balance and downstream metabolism. Structural analysis identifies key residues for cofactor binding and conformational changes.
RNA-seq and proteomics
Transcriptomic and proteomic profiling of knockout cells can reveal compensatory changes in NAD(P) metabolism and related pathways. RNA-seq identifies genes whose expression depends on NADK, while proteomics measures lipoylation status. These methods link GO:0016639 activity to broader cellular programs.
Imaging and redox sensors
Genetically encoded NADPH sensors can monitor real-time changes in cellular redox state upon modulation of GO:0016639 enzymes [1,2]. Fluorescence imaging of mitochondrial NADPH dynamics provides spatial information. These tools complement biochemical assays and help validate metabolic models.
How CRISPR Can Be Used to Study GO:0016639 oxidoreductase activity, acting on the CH-NH2 group of donors, NAD or NADP as acceptor
Knockout
CRISPR knockout of genes encoding GO:0016639 enzymes or regulators like NADK can reveal their essentiality. For example, NADK2 knockout reduces mitochondrial NADPH and impairs proline biosynthesis. LIAS knockout disrupts lipoylation and oxidative metabolism. These models are valuable for identifying metabolic vulnerabilities.
Point Mutation
Point mutations in catalytic residues of NADK or other enzymes can dissect specific functions. Based on cryo-EM structures, mutations that abolish kinase activity but preserve structure can test the role of NADP+ supply. Such models help distinguish catalytic from scaffolding functions.
Knock-in
Knock-in of tagged or mutant versions of GO:0016639 enzymes allows tracking of localization and interactions. For example, knock-in of a fluorescent tag on NADK2 can monitor mitochondrial localization. Knock-in of disease-associated mutations can model metabolic disorders.
Overexpression
Overexpression of NADK or PYCR1 can increase NADPH and proline levels, testing sufficiency in driving proliferation or stress resistance. Overexpression in cancer cell lines can model the elevated NADPH demand of tumors. These models complement knockout studies.
How EDITGENE Supports oxidoreductase activity, acting on the CH-NH2 group of donors, NAD or NADP as acceptor Research
Researchers studying oxidoreductase activity, acting on the CH-NH2 group of donors, NAD or NADP as acceptor-related genes often need to determine whether a candidate gene is causally involved in metabolic phenotypes, disease progression, or therapeutic response. EDITGENE provides CRISPR-based cell models and screening services to accelerate this discovery.
Contact EDITGENE today to design your custom CRISPR model for oxidoreductase activity, acting on the CH-NH2 group of donors, NAD or NADP as acceptor research.
Frequently Asked Questions About oxidoreductase activity, acting on the CH-NH2 group of donors, NAD or NADP as acceptor
What is GO:0016639?
GO:0016639 is a Gene Ontology molecular function term for oxidoreductase activity acting on a CH-NH2 group of donors with NAD+ or NADP as the electron acceptor [1,2].
What genes are involved in oxidoreductase activity, acting on the CH-NH2 group of donors, NAD or NADP as acceptor?
Genes include NADK, NADK2, PYCR1, PYCR2, ALDH18A1, LIAS, LIPT1, and others involved in NADPH generation and proline metabolism [1,2,4].
How is GO:0016639 related to NADPH?
Enzymes with this activity reduce NADP+ to NADPH, contributing to the cellular NADPH pool used for biosynthesis and antioxidant defense [1,2].
Why is NAD kinase important for GO:0016639?
NAD kinase produces NADP+, the cofactor required by many GO:0016639 enzymes, and its regulation controls NADP(H) balance [3,4].
What diseases are linked to GO:0016639?
Cancer metabolism, metabolic disorders with lipoylation defects, and plant stress responses are linked to this activity [2,6,7,8].
How can I study GO:0016639 in the lab?
CRISPR knockout, point mutations, metabolomics, and structural biology are common approaches [1,2,4].
What is the role of mitochondrial NADPH in proline biosynthesis?
Mitochondrial NADPH generated by enzymes like NADK2 supports proline synthesis, which is important for cell growth.
Does GO:0016639 include monoamine oxidase?
No, monoamine oxidase uses oxygen, not NAD+ or NADP, as the electron acceptor, so it is not included in GO:0016639.
What is the QuickGO definition of GO:0016639?
Catalysis of an oxidation-reduction (redox) reaction in which a CH-NH2 group acts as a hydrogen or electron donor and reduces NAD+ or NADP.
How does EDITGENE support GO:0016639 research?
EDITGENE provides knockout, point mutation, knock-in, overexpression cell models, CRISPR library screening, and bioinformatics for genes in this pathway [1,2,6].
Conclusion
GO:0016639 defines a vital class of redox enzymes that couple CH-NH2 group oxidation to NAD+ or NADP reduction. These enzymes are central to mitochondrial NADPH generation, proline biosynthesis, and lipoylation-dependent metabolism, with implications for cancer, metabolic disorders, and plant stress responses [1,2,6,7,8]. Understanding their regulation and function requires integrated genetic, structural, and metabolic approaches. EDITGENE offers comprehensive CRISPR cell models and screening services to accelerate discovery in this field.
References
- 1. Zhu J et al.. 2021. Mitochondrial NADP(H) generation is essential for proline biosynthesis.. Science 372(6545):968-972 PMID: 33888598
- 2. Kim D et al.. 2025. Mitochondrial NADPH fuels mitochondrial fatty acid synthesis and lipoylation to power oxidative metabolism.. Nat Cell Biol 27(5):790-800 PMID: 40258949
- 3. McGuinness ET et al.. 1985. NAD+ kinase--a review.. Int J Biochem 17(1):1-11 PMID: 2987053
- 4. Praharaj PP et al.. 2025. Cryo-EM structure and regulation of human NAD kinase.. Sci Adv 11(4):eads2664 PMID: 39854463
- 5. Arnon DI. 1971. The light reactions of photosynthesis.. Proc Natl Acad Sci U S A 68(11):2883-92 PMID: 4400251
- 6. Flickinger KM et al.. 2025. Cytosolic NADK is conditionally essential for folate-dependent nucleotide synthesis.. Nat Metab 7(6):1150-1167 PMID: 40316835
- 7. Akashi K et al.. 2025. Identification of CCR4C as a chloroplast-localized NADP(H) phosphatase regulating NAD(P)(H) balance in Arabidopsis.. Proc Natl Acad Sci U S A 122(42):e2504605122 PMID: 41091769
- 8. Tedeschi PM et al.. 2016. NAD+ Kinase as a Therapeutic Target in Cancer.. Clin Cancer Res 22(21):5189-5195 PMID: 27582489
