GO:0004735 pyrroline-5-carboxylate reductase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0004735 (pyrroline-5-carboxylate reductase activity) is a molecular function that catalyzes the NAD(P)H-dependent reduction of pyrroline-5-carboxylate (P5C) to proline, the final step of proline biosynthesis.
• The reaction is essential for proline homeostasis, redox balance, and cellular stress adaptation in organisms ranging from bacteria to plants and humans.
• Human PYCR1, PYCR2, and PYCR3 isoforms are implicated in cancer progression, stemness, and metabolic reprogramming.
• PYCR1 promotes liver cancer growth and metastasis via lactylation-dependent regulation of IRS1, while PYCR2 activates PI3K/AKT/mTOR signaling in colorectal cancer.
• In plants, S-nitrosylation of P5C reductase confers drought and salt tolerance, demonstrating the enzyme's role in abiotic stress responses.
• CRISPR-based knockout, point-mutation, and overexpression models are powerful tools for dissecting PYCR gene function in disease and metabolism.
Description
Pyrroline-5-carboxylate reductase (P5CR) is the enzyme responsible for the final step of proline biosynthesis, catalyzing the NAD(P)H-dependent reduction of pyrroline-5-carboxylate (P5C) to L-proline. This activity, annotated as GO:0004735, is conserved across prokaryotes, plants, and mammals, and is critical for maintaining intracellular proline pools that support protein synthesis, redox homeostasis, and stress responses. In humans, three paralogs (PYCR1, PYCR2, and PYCR3) exhibit distinct tissue distributions and kinetic properties, and their dysregulation has been linked to cancer, metabolic disorders, and developmental defects. Understanding the molecular mechanism, regulation, and disease relevance of P5CR activity is therefore of broad biomedical interest. Recent studies have demonstrated that PYCR1 drives breast cancer stemness under psychological stress, promotes liver cancer metastasis through lactylation-mediated IRS1 regulation, and that PYCR2 activates the PI3K/AKT/mTOR pathway in colorectal cancer. In plants, S-nitrosylation of P5CR enhances drought and salt tolerance, highlighting the enzyme's potential for agricultural biotechnology. This article provides a research-grade overview of GO:0004735, covering its definition, catalytic mechanism, key genes, disease associations, and experimental models for functional studies.
pyrroline-5-carboxylate reductase activity At A Glance
| GO ID | GO:0004735 |
|---|---|
| GO term | pyrroline-5-carboxylate reductase activity |
| Ontology | Molecular function (note: the provided ontology aspect is biological_process, but the term is a molecular function) |
| Synonym | None listed in QuickGO |
| Major function | Catalyzes the NAD(P)H-dependent reduction of pyrroline-5-carboxylate to L-proline, the final step of proline biosynthesis |
| EC number | 1.5.1.2 |
| Substrates | Pyrroline-5-carboxylate (P5C), NADH or NADPH |
| Products | L-proline, NAD(P)+ |
| Cofactors | NADH or NADPH |
| Localization | Cytoplasm, mitochondria (for some isoforms) |
What Is GO:0004735?
GO:0004735, pyrroline-5-carboxylate reductase activity, is a molecular function defined as the catalysis of the reaction: L-proline + NAD(P)+ = 1-pyrroline-5-carboxylate + NAD(P)H + H+. In physiological terms, the enzyme reduces P5C to proline using NADH or NADPH as an electron donor, thereby completing the proline biosynthetic pathway. This activity is essential for proline production from glutamate or arginine precursors and is reversible under certain conditions, though the biosynthetic direction is favored in vivo.
Why Is pyrroline-5-carboxylate reductase activity Important in Cell Biology?
Pyrroline-5-carboxylate reductase activity is central to proline metabolism, which influences protein synthesis, cellular redox balance, and stress adaptation. In humans, dysregulated P5CR activity contributes to cancer progression, metabolic reprogramming, and potentially neurodegenerative conditions. In plants, it is a key determinant of drought and salt tolerance. Moreover, the enzyme is a target for antimicrobial development, as shown by celastrol's inhibition of bacterial P5C dehydrogenase. Thus, understanding GO:0004735 has broad implications for cancer biology, plant biotechnology, and infectious disease research.
• Provides the final step in proline biosynthesis, essential for protein synthesis and cell growth.
• Maintains NAD(P)+/NAD(P)H balance and supports redox homeostasis.
• PYCR1 promotes breast cancer stemness under psychological stress.
• PYCR1 drives liver cancer growth and metastasis via lactylation of IRS1.
• PYCR2 activates PI3K/AKT/mTOR signaling in colorectal cancer.
• S-nitrosylation of P5CR enhances drought and salt tolerance in tomato.
• Bacterial P5C dehydrogenase, a related enzyme, is targeted by celastrol in MRSA.
• P5CR is a potential target for anti-cancer and anti-parasitic therapies.
• Kinetic studies of human P5CR inform drug design and metabolic engineering.
• The enzyme is involved in host cell invasion by Eimeria tenella, a parasite.
Molecular Mechanism of pyrroline-5-carboxylate reductase activity
Substrate Binding and Catalysis
In simple terms: The enzyme grabs P5C and a helper molecule (NADH or NADPH) and converts P5C into proline.
P5CR binds its substrate pyrroline-5-carboxylate (P5C) and a pyridine nucleotide cofactor (NADH or NADPH) in a sequential ordered mechanism. The enzyme catalyzes the transfer of hydride from the cofactor to the C1 carbon of P5C, followed by protonation to form L-proline. Kinetic studies of human PYCR isoforms have revealed differences in cofactor preference and catalytic efficiency, with PYCR1 favoring NADH and PYCR2 utilizing both NADH and NADPH.
Cofactor Specificity and Redox Regulation
In simple terms: Different versions of the enzyme prefer different helper molecules, which affects how they work in cells.
Human PYCR1, PYCR2, and PYCR3 exhibit distinct cofactor preferences. PYCR1 primarily uses NADH, while PYCR2 can utilize both NADH and NADPH, and PYCR3 is less characterized. This specificity influences the enzyme's role in cellular redox balance, as NADPH is a key reducing agent in biosynthesis and antioxidant defense. The NAD(P)H/NAD(P)+ ratio can modulate P5CR activity, linking proline synthesis to metabolic state.
Isoform Diversity and Tissue Distribution
In simple terms: There are three main versions of this enzyme in humans, and they are found in different tissues and have different jobs.
In humans, three genes encode P5CR isoforms: PYCR1, PYCR2, and PYCR3. PYCR1 is localized to mitochondria and is highly expressed in many tissues, PYCR2 is cytosolic and abundant in the brain, and PYCR3 is testis-specific. These isoforms differ in kinetic properties, regulation, and subcellular localization, contributing to tissue-specific proline metabolism. For example, PYCR1 promotes cancer stemness in breast cancer, while PYCR2 activates oncogenic signaling in colorectal cancer.
Post-translational Modifications and Regulation
In simple terms: The enzyme can be chemically modified, which changes how active it is.
P5CR activity is regulated by post-translational modifications. In tomato, S-nitrosylation of P5CR at a specific cysteine residue enhances its activity and confers drought and salt tolerance. In liver cancer, PYCR1 is lactylated, which affects its interaction with IRS1 and promotes metastasis. These modifications allow fine-tuning of proline synthesis in response to cellular stress and metabolic cues.
Role in Proline Biosynthesis and Stress Response
In simple terms: This enzyme makes proline, which helps cells survive stress like drought or high salt.
P5CR catalyzes the final step of proline biosynthesis from glutamate or arginine. Proline accumulates under osmotic stress, acting as a compatible osmolyte and reactive oxygen species scavenger. In plants, overexpression of P5CR or its modified forms improves drought and salt tolerance. In mammalian cells, proline supports cancer cell growth and stemness under stress conditions.
Key Genes Involved in GO:0004735 pyrroline-5-carboxylate reductase activity
The following genes encode enzymes with pyrroline-5-carboxylate reductase activity or are directly involved in its regulation and downstream effects.
| Gene | Major Role | Research Relevance |
|---|---|---|
| PYCR1 | Mitochondrial P5CR isoform; catalyzes P5C to proline | Promotes liver cancer growth and metastasis via lactylation of IRS1; drives breast cancer stemness under stress |
| PYCR2 | Cytosolic P5CR isoform; proline biosynthesis | Activates PI3K/AKT/mTOR pathway in colorectal cancer |
| PYCR3 | Testis-specific P5CR isoform | Less studied; potential role in male fertility and cancer |
| PRODH | Proline dehydrogenase; catalyzes reverse reaction | Regulates proline catabolism and redox balance |
| P5CS | Delta-1-pyrroline-5-carboxylate synthetase; produces P5C | Upstream of P5CR in proline biosynthesis |
| OAT | Ornithine aminotransferase; produces P5C from ornithine | Alternative route for P5C generation |
| SIRT3 | Mitochondrial deacetylase; regulates mitochondrial homeostasis | Activator 2-APQC alleviates myocardial hypertrophy via SIRT3 |
| IRS1 | Insulin receptor substrate 1; signaling adaptor | Regulated by PYCR1 lactylation in liver cancer |
| mTOR | Kinase; central regulator of cell growth | Activated downstream of PYCR2 in colorectal cancer |
| PI3K | Phosphoinositide 3-kinase; signaling | Activated by PYCR2 in colorectal cancer |
| AKT | Serine/threonine kinase; signaling | Activated by PYCR2 in colorectal cancer |
| P5CDH | P5C dehydrogenase; oxidizes P5C to glutamate | Target of celastrol in MRSA |
| Eimeria tenella P5CR | Parasite P5CR; secreted protein | Involved in host cell invasion |
| Tomato P5CR | Plant P5CR; proline biosynthesis | S-nitrosylation enhances drought and salt tolerance |
| Celastrol | Small molecule inhibitor of P5CDH | Combats methicillin-resistant Staphylococcus aureus |
| 2-APQC | Small-molecule activator of SIRT3 | Alleviates myocardial hypertrophy and fibrosis |
How Is pyrroline-5-carboxylate reductase activity Regulated?
P5CR activity is regulated at multiple levels. Transcriptional regulation of PYCR genes responds to stress and metabolic signals. Post-translational modifications, including S-nitrosylation in plants and lactylation in human cancer, directly modulate enzyme activity and interactions. Cofactor availability (NADH/NADPH) influences catalytic rate. In cancer, oncogenic signaling pathways such as PI3K/AKT/mTOR are activated downstream of PYCR2, suggesting feedback regulation. Additionally, mitochondrial homeostasis regulators like SIRT3 can impact proline metabolism through effects on mitochondrial function.
pyrroline-5-carboxylate reductase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| PYCR1 | Liver cancer growth and metastasis | Knockout or overexpression in liver cancer cell lines |
| PYCR1 | Breast cancer stemness under stress | Knockout in breast cancer cells under psychological stress |
| PYCR2 | Colorectal cancer progression | Knockout or overexpression in colorectal cancer cells |
| P5CDH (bacterial) | MRSA infection | Bacterial knockout and celastrol treatment |
| Eimeria tenella P5CR | Host cell invasion | Parasite knockout or knockdown |
Cancer
PYCR1 and PYCR2 are overexpressed in multiple cancers and promote tumor growth, metastasis, and stemness. In liver cancer, PYCR1 lactylation enhances its interaction with IRS1, leading to increased proliferation and metastasis. In breast cancer, PYCR1 reprograms proline metabolism to drive cancer stemness under psychological stress. PYCR2 activates the PI3K/AKT/mTOR pathway in colorectal cancer, supporting progression. These findings highlight P5CR as a potential therapeutic target.
Metabolic and Cardiovascular Disorders
Proline metabolism is linked to mitochondrial function and redox balance. The SIRT3 activator 2-APQC alleviates myocardial hypertrophy and fibrosis by regulating mitochondrial homeostasis, suggesting that P5CR activity may influence cardiac pathology through mitochondrial pathways. However, direct evidence for P5CR in cardiovascular disease is limited.
Infectious Diseases
Bacterial P5C dehydrogenase, which catalyzes the reverse of P5CR, is targeted by celastrol in methicillin-resistant Staphylococcus aureus. In the parasite Eimeria tenella, P5CR is a secreted protein involved in host cell invasion, indicating a role in pathogenesis. These findings suggest that P5CR and related enzymes are potential antimicrobial targets.
Plant Stress and Agriculture
In tomato, S-nitrosylation of P5CR enhances drought and salt tolerance. This demonstrates the importance of P5CR in plant stress responses and its potential for genetic engineering to improve crop resilience.
From pyrroline-5-carboxylate reductase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does PYCR1 loss reduce liver cancer metastasis? | PYCR1 knockout in liver cancer cell lines and mouse xenografts |
| Does PYCR1 lactylation affect IRS1 interaction? | Point mutation of lactylation sites in PYCR1 |
| Does PYCR2 activate PI3K/AKT/mTOR? | PYCR2 knockout and overexpression in colorectal cancer cells |
| Does S-nitrosylation of P5CR enhance stress tolerance? | Knock-in of cysteine mutant in tomato |
| Is P5CR secreted by Eimeria tenella? | Tagged knock-in of P5CR in parasite |
| Can SIRT3 activation rescue cardiac hypertrophy? | Overexpression of SIRT3 or treatment with 2-APQC |
How to Study the pyrroline-5-carboxylate reductase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Enzymatic assay | P5CR catalytic activity | Kinetic characterization of isoforms and mutants |
| Metabolomics | Proline and P5C levels | Assessing metabolic flux changes |
| Co-IP / Western blot | Protein interactions and modifications | Validating lactylation or S-nitrosylation |
| CRISPR knockout screen | Gene essentiality and synthetic lethality | Identifying P5CR dependencies in cancer |
| RNA-seq | Transcriptional changes | Measuring PYCR gene expression under stress |
| Immunofluorescence | Subcellular localization | Determining mitochondrial vs cytosolic isoforms |
| Xenograft models | Tumor growth and metastasis | Testing PYCR1 knockout in vivo |
Enzymatic Activity Assays
P5CR activity is typically measured spectrophotometrically by monitoring the oxidation of NAD(P)H at 340 nm in the presence of P5C. Kinetic parameters (Km, Vmax) can be determined for different isoforms and mutants. This method is essential for validating the functional impact of CRISPR edits.
Metabolic Profiling
Mass spectrometry-based metabolomics can quantify proline, P5C, and related metabolites in cells and tissues. This approach reveals how genetic perturbations alter flux through the proline biosynthetic pathway.
Protein Interaction and Modification Studies
Co-immunoprecipitation, Western blotting, and mass spectrometry can identify interacting partners (e.g., IRS1) and post-translational modifications (e.g., lactylation, S-nitrosylation) of P5CR. These methods help elucidate regulatory mechanisms.
CRISPR Screening and Functional Genomics
Genome-wide CRISPR knockout screens can identify genes that modulate P5CR dependency in cancer cells. Such screens are powerful for discovering synthetic lethal interactions and resistance mechanisms.
How CRISPR Can Be Used to Study GO:0004735 pyrroline-5-carboxylate reductase activity
Knockout
CRISPR knockout of PYCR1, PYCR2, or PYCR3 can abolish P5CR activity, leading to reduced proline levels and impaired cell growth under stress. Knockout models are used to study cancer cell dependency and metabolic reprogramming.
Point Mutation
Point mutations can be introduced to disrupt specific residues involved in catalysis, cofactor binding, or post-translational modifications (e.g., lactylation sites in PYCR1 or S-nitrosylation sites in plant P5CR). These models help dissect the functional significance of individual modifications.
Knock-in
Knock-in of tagged P5CR (e.g., FLAG, GFP) allows for localization, interaction, and purification studies. Knock-in of disease-associated variants can model human disorders. In plants, knock-in of S-nitrosylation-resistant mutants can test stress tolerance.
Overexpression
Overexpression of PYCR isoforms or mutant versions can drive proline accumulation, promote cancer stemness, or activate signaling pathways. Overexpression models are useful for gain-of-function studies and drug screening.
How EDITGENE Supports pyrroline-5-carboxylate reductase activity Research
Researchers studying pyrroline-5-carboxylate reductase activity-related genes often need to determine whether a candidate gene is causally involved in a specific phenotype, such as cancer progression or stress tolerance. EDITGENE provides comprehensive CRISPR-based services to generate precisely engineered cell models for such functional studies.
Contact EDITGENE today to design your custom CRISPR model for pyrroline-5-carboxylate reductase activity research.
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| PYCR1 Knockout HEK293 Cell Line | EDJ-KQ3381 | Human | 5831 | Details Get a Quote |
| NOXRED1 Knockout HEK293 Cell Line | EDJ-KQ8166 | Human | 122945 | Details Get a Quote |
| PYCR3 Knockout HEK293 Cell Line | EDJ-KQ14963 | Human | 65263 | Details Get a Quote |
| PYCR1 Knockout A-549 Cell Line | EDJ-KQ25065 | Human | 5831 | Details Get a Quote |
| PYCR1 Knockout HCT 116 Cell Line | EDJ-KQ25066 | Human | 5831 | Details Get a Quote |
| PYCR1 Knockout HeLa Cell Line | EDJ-KQ23678 | Human | 5831 | Details Get a Quote |
| PYCR3 Knockout A-549 Cell Line | EDJ-KQ45441 | Human | 65263 | Details Get a Quote |
| PYCR3 Knockout HCT 116 Cell Line | EDJ-KQ45442 | Human | 65263 | Details Get a Quote |
| PYCR3 Knockout HeLa Cell Line | EDJ-KQ45443 | Human | 65263 | Details Get a Quote |
| PYCR2 Knockout HEK293 Cell Line | EDJ-KQ51244 | Human | 29920 | Details Get a Quote |
| PYCR2 Knockout HeLa Cell Line | EDJ-KQ56121 | Human | 29920 | Details Get a Quote |
| NOXRED1 Knockout HeLa Cell Line | EDJ-KQ58111 | Human | 122945 | Details Get a Quote |
| PYCR2 Knockout A-549 Cell Line | EDJ-KQ64607 | Human | 29920 | Details Get a Quote |
| NOXRED1 Knockout A-549 Cell Line | EDJ-KQ66599 | Human | 122945 | Details Get a Quote |
| PYCR2 Knockout HCT 116 Cell Line | EDJ-KQ73059 | Human | 29920 | Details Get a Quote |
Displaying Records 1 To 15 Of 16 Records
Frequently Asked Questions About pyrroline-5-carboxylate reductase activity
What is pyrroline-5-carboxylate reductase activity?
It is the enzymatic activity (GO:0004735) that catalyzes the NAD(P)H-dependent reduction of pyrroline-5-carboxylate to L-proline, the final step of proline biosynthesis.
What genes are involved in pyrroline-5-carboxylate reductase activity?
In humans, the main genes are PYCR1, PYCR2, and PYCR3, which encode distinct isoforms with different tissue distributions and kinetic properties.
What diseases are associated with pyrroline-5-carboxylate reductase activity?
Dysregulation of PYCR genes is linked to cancer (liver, breast, colorectal), and the enzyme is a potential target for antimicrobial and plant biotechnology applications.
How is pyrroline-5-carboxylate reductase activity regulated?
It is regulated by cofactor availability, post-translational modifications such as lactylation and S-nitrosylation, and transcriptional changes in response to stress.
What is the role of PYCR1 in cancer?
PYCR1 promotes liver cancer growth and metastasis via lactylation-dependent regulation of IRS1, and drives breast cancer stemness under psychological stress.
How can I study pyrroline-5-carboxylate reductase activity using CRISPR?
CRISPR knockout, point mutation, knock-in, and overexpression models can be used to dissect gene function, metabolic pathways, and disease relevance.
What is the difference between PYCR1 and PYCR2?
PYCR1 is mitochondrial and prefers NADH, while PYCR2 is cytosolic, can use both NADH and NADPH, and activates PI3K/AKT/mTOR in colorectal cancer.
Is pyrroline-5-carboxylate reductase activity important in plants?
Yes, S-nitrosylation of P5CR enhances drought and salt tolerance in tomato, highlighting its role in stress adaptation.
What experimental models are available for P5CR research?
Models include CRISPR knockout cell lines, point mutants, tagged knock-ins, overexpression lines, and xenograft mouse models.
Can pyrroline-5-carboxylate reductase be targeted for antimicrobial therapy?
Bacterial P5C dehydrogenase, which catalyzes the reverse reaction, is targeted by celastrol in MRSA, suggesting related enzymes are druggable.
Conclusion
Pyrroline-5-carboxylate reductase activity (GO:0004735) is a fundamental enzymatic function that bridges proline metabolism, redox balance, and stress responses. Its dysregulation is implicated in cancer, metabolic disorders, and infectious diseases, making it a compelling target for therapeutic intervention. In plants, it offers opportunities for improving crop resilience. With the advent of CRISPR-based genome editing, researchers can now precisely manipulate PYCR genes to uncover their mechanistic roles and validate them as drug targets. EDITGENE's comprehensive services empower such discoveries.
References
- 1. Yuan Z et al.. 2023. Celastrol Combats Methicillin-Resistant Staphylococcus aureus by Targeting Δ(1) -Pyrroline-5-Carboxylate Dehydrogenase.. Adv Sci (Weinh) 10(25):e2302459 PMID: 37381655
- 2. Peng F et al.. 2024. 2-APQC, a small-molecule activator of Sirtuin-3 (SIRT3), alleviates myocardial hypertrophy and fibrosis by regulating mitochondrial homeostasis.. Signal Transduct Target Ther 9(1):133 PMID: 38744811
- 3. Wang H et al.. 2024. PYCR1 promotes liver cancer cell growth and metastasis by regulating IRS1 expression through lactylation modification.. Clin Transl Med 14(10):e70045 PMID: 39422696
- 4. Patel SM et al.. 2021. Kinetics of human pyrroline-5-carboxylate reductase in L-thioproline metabolism.. Amino Acids 53(12):1863-1874 PMID: 34792644
- 5. Cui B et al.. 2023. Pyrroline-5-carboxylate reductase 1 reprograms proline metabolism to drive breast cancer stemness under psychological stress.. Cell Death Dis 14(10):682 PMID: 37845207
- 6. Liang S et al.. 2024. Eimeria tenella pyrroline -5-carboxylate reductase is a secreted protein and involved in host cell invasion.. Exp Parasitol 259:108712 PMID: 38336093
- 7. Yin F et al.. 2021. Pyrroline-5-Carboxylate Reductase-2 Promotes Colorectal Cancer Progression via Activating PI3K/AKT/mTOR Pathway.. Dis Markers 2021:9950663 PMID: 34512817
- 8. Liu W et al.. 2024. Genetic engineering of drought- and salt-tolerant tomato via Δ1-pyrroline-5-carboxylate reductase S-nitrosylation.. Plant Physiol 195(2):1038-1052 PMID: 38478428
