GO:0018454 acetoacetyl-CoA reductase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0018454 acetoacetyl-CoA reductase activity catalyzes the reversible NADPH-dependent reduction of 3-oxoacyl-CoA to (R)-3-hydroxyacyl-CoA.
• The enzyme is a short-chain dehydrogenase/reductase (SDR) that uses NADPH or NADH as a cofactor, with cofactor preference tunable by protein engineering.
• Acetoacetyl-CoA reductase is best characterized in polyhydroxyalkanoate (PHA)-producing bacteria such as Cupriavidus necator and Zoogloea ramigera.
• In mammals, acetoacetyl-CoA reductase activity is associated with fatty acid synthase and with a distinct hepatic microsomal beta-ketoacyl-CoA reductase.
• The enzyme provides the (R)-3-hydroxyacyl-CoA precursor for polyhydroxybutyrate (PHB) biosynthesis and contributes to ketone body and lipid metabolism.
• CRISPR knockout, point-mutation, knock-in, and overexpression models enable causal dissection of acetoacetyl-CoA reductase function in metabolism and disease.
Description
Acetoacetyl-CoA reductase activity (GO:0018454) is a molecular function defined as the catalysis of the reaction (R)-3-hydroxyacyl-CoA + NADP+ = 3-oxoacyl-CoA + NADPH + H+. This oxidoreductase activity sits at the intersection of ketone body metabolism, fatty acid synthesis, and microbial polyhydroxyalkanoate (PHA) biosynthesis, making it a focal point for metabolic engineering and for understanding lipid-related disease. The enzyme is widely distributed across bacteria, plants, and mammals, and its cofactor specificity (NADPH versus NADH) is a key determinant of its physiological role. Researchers study GO:0018454 to engineer microbial production of biodegradable plastics, to probe hepatic lipid metabolism, and to understand how cells balance reducing equivalents. The reaction is reversible in vitro, but in vivo it typically functions in the reductive direction to supply (R)-3-hydroxyacyl-CoA for downstream pathways. Because the enzyme belongs to the short-chain dehydrogenase/reductase (SDR) superfamily, its mechanism, substrate specificity, and cofactor preference have been dissected using purified recombinant proteins and site-directed mutagenesis. This article integrates authoritative QuickGO annotation with verified PubMed literature to summarize the mechanism, key genes, disease links, and CRISPR-based research methods for GO:0018454. It is intended for researchers seeking a concise, citation-backed overview that supports experimental design and generative-AI retrieval.
acetoacetyl-CoA reductase activity At A Glance
| GO ID | GO:0018454 |
|---|---|
| GO term | acetoacetyl-CoA reductase activity |
| Ontology | molecular_function |
| Synonym | acetoacetyl coenzyme A reductase activity; beta-ketoacyl-CoA reductase; D-3-hydroxyacyl-CoA reductase activity; NADPH:acetoacetyl-CoA reductase activity; (R)-3-hydroxyacyl-CoA dehydrogenase activity |
| Major function | Catalyzes the reversible NADPH-dependent reduction of 3-oxoacyl-CoA to (R)-3-hydroxyacyl-CoA |
| Reaction | (R)-3-hydroxyacyl-CoA + NADP+ = 3-oxoacyl-CoA + NADPH + H+ |
| Cofactor | NADPH (preferred in many homologs); NADH in some bacterial enzymes |
| Substrate | Acetoacetyl-CoA and other short-chain 3-oxoacyl-CoA thioesters |
| Enzyme family | Short-chain dehydrogenase/reductase (SDR) superfamily |
| Biological context | Polyhydroxyalkanoate biosynthesis, ketone body metabolism, fatty acid synthesis |
What Is GO:0018454?
GO:0018454 acetoacetyl-CoA reductase activity is defined by QuickGO as the catalysis of the reaction: (R)-3-hydroxyacyl-CoA + NADP+ = 3-oxoacyl-CoA + NADPH + H+. In other words, the enzyme transfers a hydride from NADPH to the beta-keto group of a 3-oxoacyl-CoA substrate, producing the corresponding (R)-3-hydroxyacyl-CoA and NADP+. The reaction is reversible, and the enzyme can also accept NADH in some homologs, albeit often with lower efficiency under physiological conditions. The activity is synonymous with acetoacetyl coenzyme A reductase, beta-ketoacyl-CoA reductase, D-3-hydroxyacyl-CoA reductase, and NADPH:acetoacetyl-CoA reductase, reflecting its broad substrate range and historical naming.
Why Is acetoacetyl-CoA reductase activity Important in Cell Biology?
GO:0018454 is important because it controls the flux of carbon into (R)-3-hydroxyacyl-CoA, a central metabolite for polyhydroxyalkanoate (PHA) biosynthesis in bacteria and for ketone body and fatty acid metabolism in mammals. In biotechnology, engineering acetoacetyl-CoA reductase cofactor preference is a proven strategy to improve NADH-dependent PHA production under physiological conditions. In medicine, the enzyme's activity has been linked to hepatic lipid handling and to the fatty acid synthase complex, making it relevant to metabolic disorders and cancer metabolism. Understanding its mechanism and regulation is therefore essential for both industrial and biomedical research.
• Provides the (R)-3-hydroxyacyl-CoA precursor for polyhydroxybutyrate (PHB) and other PHA biopolymers.
• Contributes to ketone body metabolism and hepatic lipid homeostasis.
• Is a target for metabolic engineering of NADH-preferring enzymes for anaerobic bioproduction.
• Serves as a model SDR enzyme for studying cofactor specificity and catalytic mechanism.
• Links to fatty acid synthase activity in lactating mammary tissue.
• Distinct from long-chain beta-ketoacyl-CoA reductase in microsomal fatty acid elongation.
• Relevant to cancer metabolism due to altered lipid synthesis pathways.
• Enables production of biodegradable plastics from renewable feedstocks.
• Provides a selectable metabolic marker in recombinant E. coli expression systems.
• Supports studies of redox balance and NADPH/NADH homeostasis.
Molecular Mechanism of acetoacetyl-CoA reductase activity
Substrate binding and orientation
In simple terms: The enzyme grabs acetoacetyl-CoA and positions it next to NADPH.
Acetoacetyl-CoA reductase binds its 3-oxoacyl-CoA substrate in a pocket that positions the beta-keto carbon for hydride transfer from the nicotinamide ring of NADPH. The enzyme accepts short-chain 3-oxoacyl-CoA thioesters, with acetoacetyl-CoA being the best-characterized substrate. Substrate specificity is determined by the acyl-binding tunnel, which excludes long-chain substrates.
Hydride transfer and stereochemistry
In simple terms: NADPH hands a hydrogen to the substrate, making a specific mirror-image product.
The catalytic mechanism involves direct hydride transfer from the pro-S face of NADPH to the si face of the substrate carbonyl, yielding the (R)-3-hydroxyacyl-CoA product. This stereospecificity is a hallmark of the SDR family and has been confirmed by mechanistic studies of the cloned Zoogloea ramigera enzyme overproduced in Escherichia coli. The reaction is reversible, but the equilibrium favors the reductive direction under physiological NADPH/NADP+ ratios.
Cofactor specificity and engineering
In simple terms: Some versions of the enzyme prefer NADH over NADPH, and scientists can change that preference.
While many acetoacetyl-CoA reductases are NADPH-dependent, some bacterial homologs use NADH. Engineering the Cupriavidus necator enzyme toward NADH preference under physiological conditions has been achieved by mutating residues in the cofactor-binding pocket, demonstrating that cofactor specificity is tunable. This is important for industrial strains where NADH is more abundant than NADPH.
Enzyme family and structural features
In simple terms: The enzyme belongs to a large family of similar proteins with a common fold.
Acetoacetyl-CoA reductase is a member of the short-chain dehydrogenase/reductase (SDR) superfamily, characterized by a Rossmann-fold NAD(P)-binding domain and a catalytic triad of Asn-Ser-Tyr-Lys residues. The enzyme typically functions as a homodimer or homotetramer, and its quaternary structure is required for full activity. Recombinant expression with His-tags has facilitated purification and characterization of the enzyme from various sources.
Physiological context and regulation
In simple terms: The enzyme works as part of larger metabolic pathways and its levels are controlled by the cell.
In bacteria, acetoacetyl-CoA reductase supplies (R)-3-hydroxyacyl-CoA for PHA synthase in polyhydroxybutyrate biosynthesis. In mammals, the activity is associated with fatty acid synthase in lactating mammary tissue and with a distinct hepatic microsomal beta-ketoacyl-CoA reductase involved in fatty acid elongation. Expression of the enzyme is regulated by metabolic signals and substrate availability, though specific transcriptional regulators remain to be fully defined.
Key Genes Involved in GO:0018454 acetoacetyl-CoA reductase activity
The following genes and proteins are experimentally linked to acetoacetyl-CoA reductase activity (GO:0018454) based on the verified literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| phaB (Cupriavidus necator) | NADPH-dependent acetoacetyl-CoA reductase in PHB biosynthesis | Engineered for NADH preference to improve PHA production |
| phaB (Zoogloea ramigera) | NADP-linked acetoacetyl-CoA reductase | Model enzyme for mechanistic and structural studies |
| phbB (Zoogloea ramigera) | NADPH-linked acetoacetyl-CoA reductase | Cloned and overproduced in E. coli for characterization |
| FASN (bovine) | Fatty acid synthase with intrinsic acetoacetyl-CoA reductase activity | Studied in lactating mammary tissue |
| Hsd17b8 (rat) | Microsomal beta-ketoacyl-CoA reductase | Distinct from long-chain elongase component |
| fabG (E. coli) | 3-oxoacyl-ACP reductase, related SDR | Comparative studies of SDR mechanism |
| phaA (C. necator) | Beta-ketothiolase, upstream of PhaB | Pathway engineering for PHA |
| phaC (C. necator) | PHA synthase, downstream of PhaB | Polymer production |
| SDR family members | General short-chain dehydrogenases/reductases | Cofactor specificity studies |
| NADPH-dependent reductases | Various metabolic roles | Redox balance research |
| His-tagged PhaB | Recombinant enzyme for purification | Expression in E. coli BL-21(DE3) |
| Bovine FASN | Multifunctional enzyme complex | Acetoacetyl-CoA reductase activity in fatty acid synthesis |
| Rat hepatic microsomal reductase | Beta-ketoacyl-CoA reductase | Fatty acid elongation system |
| Zoogloea ramigera I-16-M | Native source of NADP-linked enzyme | Purification and characterization |
| Cupriavidus necator | Native source of NADPH-dependent enzyme | Engineering studies |
| E. coli BL-21(DE3) | Heterologous expression host | Recombinant protein production |
| NADP+ | Oxidized cofactor | Enzyme assays |
| NADPH | Reduced cofactor | Enzyme assays |
How Is acetoacetyl-CoA reductase activity Regulated?
Acetoacetyl-CoA reductase activity is regulated at multiple levels. In bacteria, expression of phaB is controlled by the availability of carbon sources and by the cellular redox state, with NADPH/NADP+ ratios influencing flux through the pathway. The enzyme's cofactor preference can be altered by single amino acid substitutions, which effectively changes its regulation by the cellular redox environment. In mammals, the activity associated with fatty acid synthase is regulated by nutritional and hormonal signals that control lipogenesis. The distinct hepatic microsomal beta-ketoacyl-CoA reductase is regulated independently of the long-chain elongase component, suggesting separate physiological roles. Post-translational modifications and allosteric regulation have not been extensively characterized for this enzyme, representing a gap in current knowledge.
acetoacetyl-CoA reductase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| FASN | Cancer, obesity, fatty liver | Knockout in HepG2 cells; point mutation of reductase domain |
| Hsd17b8 | Lipid metabolism disorders | Liver-specific knockout in mice |
| phaB (C. necator) | Bacterial stress resistance | Knockout in C. necator; complementation |
| phaB (Z. ramigera) | PHA biosynthesis | Overexpression in E. coli |
| SDR family | Inherited metabolic diseases | CRISPR knock-in of patient variants |
Metabolic disorders and hepatic lipid metabolism
Acetoacetyl-CoA reductase activity contributes to hepatic lipid handling, and its association with fatty acid synthase and microsomal beta-ketoacyl-CoA reductase suggests a role in fatty liver disease and dyslipidemia. The enzyme's product, (R)-3-hydroxyacyl-CoA, is a precursor for ketone bodies and complex lipids, linking its activity to energy homeostasis. Experimental models with altered enzyme levels could clarify its contribution to steatosis and insulin resistance.
Cancer metabolism
Cancer cells often exhibit increased lipogenesis, and enzymes involved in fatty acid synthesis, including acetoacetyl-CoA reductase activity associated with FASN, are upregulated in several tumors. Targeting this activity could disrupt membrane synthesis and energy production in cancer cells. However, direct evidence linking GO:0018454 to specific cancers remains limited and requires further study.
Infectious disease and microbial pathogenesis
Polyhydroxyalkanoate biosynthesis, which depends on acetoacetyl-CoA reductase, contributes to the survival and stress resistance of pathogenic bacteria such as Pseudomonas aeruginosa. Inhibiting this enzyme could reduce virulence and biofilm formation, though no specific inhibitors are currently in clinical use.
From acetoacetyl-CoA reductase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of acetoacetyl-CoA reductase affect PHA production? | CRISPR knockout of phaB in Cupriavidus necator |
| Can cofactor preference be switched from NADPH to NADH? | Point mutation of cofactor-binding residues in phaB |
| What is the effect of a disease-associated variant? | Knock-in of the variant into the endogenous locus |
| Where is the enzyme localized in mammalian cells? | Tagged knock-in with fluorescent protein |
| Does overexpression increase lipid accumulation? | Overexpression of FASN or Hsd17b8 in hepatocytes |
| Is the enzyme essential for bacterial growth? | CRISPR interference knockdown in E. coli |
How to Study the acetoacetyl-CoA reductase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| NADPH oxidation assay | Enzyme activity | Kinetic characterization |
| His-tag purification | Protein purity and yield | Recombinant enzyme production |
| Site-directed mutagenesis | Cofactor specificity | Protein engineering |
| CRISPR knockout | Loss-of-function phenotype | Metabolic pathway analysis |
| CRISPR knock-in | Variant function | Disease modeling |
| Western blot | Protein expression levels | Overexpression validation |
| GC-MS | PHA polymer composition | Biopolymer production |
Enzymatic assays
Acetoacetyl-CoA reductase activity is typically measured spectrophotometrically by monitoring the oxidation of NADPH at 340 nm in the presence of acetoacetyl-CoA. This method allows determination of kinetic parameters such as Km and Vmax for both substrates and cofactors. Radioactive assays using labeled acetoacetyl-CoA can provide higher sensitivity for crude extracts.
Recombinant protein production and purification
His-tagged acetoacetyl-CoA reductase can be expressed in Escherichia coli BL-21(DE3) and purified by nickel-affinity chromatography, enabling detailed biochemical and structural studies. This approach has been used to characterize the Zoogloea ramigera enzyme and to perform mechanistic studies.
Site-directed mutagenesis and protein engineering
Mutating specific residues in the cofactor-binding pocket can alter NADPH/NADH preference, as demonstrated for the Cupriavidus necator enzyme. This method is essential for tailoring the enzyme for industrial applications and for probing structure-function relationships.
CRISPR-based genome editing
CRISPR knockout, knock-in, and point mutation models allow causal testing of acetoacetyl-CoA reductase function in native contexts. These models are particularly useful for studying metabolic flux and for validating drug targets.
How CRISPR Can Be Used to Study GO:0018454 acetoacetyl-CoA reductase activity
Knockout
CRISPR knockout of phaB in Cupriavidus necator or other PHA-producing bacteria abolishes acetoacetyl-CoA reductase activity, leading to loss of polyhydroxybutyrate accumulation. In mammalian cells, knockout of Hsd17b8 or FASN can disrupt lipid metabolism and reveal the enzyme's contribution to hepatic steatosis. Knockout models are essential for establishing causality in metabolic pathways.
Point Mutation
Point mutations in the cofactor-binding pocket of phaB can switch NADPH preference to NADH, as demonstrated by engineering the Cupriavidus necator enzyme. Such mutations are introduced via CRISPR base editing or homology-directed repair to study the effect of specific residues on catalysis and cofactor specificity. This approach is valuable for both mechanistic studies and strain optimization.
Knock-in
Knock-in of disease-associated variants or tagged versions of acetoacetyl-CoA reductase allows study of protein localization, stability, and function in a physiological context. For example, knocking in a fluorescent tag at the endogenous Hsd17b8 locus enables live-cell imaging of the microsomal reductase. Knock-in models are also used to humanize bacterial enzymes for drug discovery.
Overexpression
Overexpression of acetoacetyl-CoA reductase, often with an N-terminal His-tag, is used to produce large quantities of recombinant enzyme for biochemical and structural studies. In metabolic engineering, overexpression of phaB together with phaA and phaC increases PHA yield in recombinant E. coli. Overexpression in mammalian cells can also model the effects of increased lipogenesis.
How EDITGENE Supports acetoacetyl-CoA reductase activity Research
Researchers studying acetoacetyl-CoA reductase activity-related genes often need to determine whether a candidate gene is causally involved in a metabolic pathway or disease phenotype. EDITGENE provides a comprehensive suite of CRISPR-based services to generate precisely engineered cell models, enabling rigorous functional validation of GO:0018454 and its associated genes.
Contact EDITGENE today to design your custom CRISPR model for acetoacetyl-CoA reductase activity research.
Frequently Asked Questions About acetoacetyl-CoA reductase activity
What is acetoacetyl-CoA reductase activity?
Acetoacetyl-CoA reductase activity (GO:0018454) is the catalysis of the reversible NADPH-dependent reduction of 3-oxoacyl-CoA to (R)-3-hydroxyacyl-CoA, as defined by QuickGO.
What genes are involved in acetoacetyl-CoA reductase activity?
Key genes include phaB from Cupriavidus necator and Zoogloea ramigera, FASN in mammals, and Hsd17b8 in rat liver.
What is the reaction catalyzed by GO:0018454?
The reaction is (R)-3-hydroxyacyl-CoA + NADP+ = 3-oxoacyl-CoA + NADPH + H+.
Which cofactor does acetoacetyl-CoA reductase use?
Most characterized enzymes prefer NADPH, but some bacterial homologs use NADH, and cofactor preference can be engineered.
What is the role of acetoacetyl-CoA reductase in polyhydroxybutyrate synthesis?
It supplies (R)-3-hydroxyacyl-CoA for PHA synthase, the key precursor for polyhydroxybutyrate biosynthesis.
How is acetoacetyl-CoA reductase activity measured?
It is typically measured spectrophotometrically by monitoring NADPH oxidation at 340 nm in the presence of acetoacetyl-CoA.
Is acetoacetyl-CoA reductase linked to human disease?
It is associated with hepatic lipid metabolism and cancer through FASN, but direct disease links require further study.
Can CRISPR be used to study acetoacetyl-CoA reductase?
Yes, CRISPR knockout, knock-in, point mutation, and overexpression models enable functional studies of GO:0018454.
What is the difference between acetoacetyl-CoA reductase and beta-ketoacyl-CoA reductase?
Acetoacetyl-CoA reductase (GO:0018454) acts on short-chain substrates, while the microsomal beta-ketoacyl-CoA reductase is distinct and involved in long-chain fatty acid elongation.
How can I engineer acetoacetyl-CoA reductase for NADH preference?
Site-directed mutagenesis of cofactor-binding residues can switch preference from NADPH to NADH, as shown for the Cupriavidus necator enzyme.
Conclusion
Acetoacetyl-CoA reductase activity (GO:0018454) is a versatile oxidoreductase that bridges ketone body metabolism, fatty acid synthesis, and microbial biopolymer production. Its mechanism, cofactor specificity, and physiological roles have been elucidated through biochemical, structural, and genetic studies. CRISPR-based models now offer powerful tools to dissect its function in health and disease, and EDITGENE provides end-to-end services to support such research.
References
- 1. Olavarria K et al.. 2022. Engineering an acetoacetyl-CoA reductase from Cupriavidus necator toward NADH preference under physiological conditions.. Sci Rep 12(1):3757 PMID: 35260659
- 2. Kee PE et al.. 2023. Expression of His-tagged NADPH-dependent acetoacetyl-CoA reductase in recombinant Escherichia coli BL-21(DE3).. J Biosci Bioeng 136(4):312-319 PMID: 37500302
- 3. Dodds PF et al.. 1981. Acetoacetyl-CoA reductase activity of lactating bovine mammary fatty acid synthase.. J Biol Chem 256(12):6282-90 PMID: 7016867
- 4. Shuto H et al.. 1981. An NAD-linked acetoacetyl-CoA reductase from Zoogloea ramigera I-16-M.. Eur J Biochem 118(1):53-9 PMID: 7026239
- 5. Saito T et al.. 1977. An NADP-linked acetoacetyl CoA reductase from Zoogloea ramigera.. Arch Microbiol 114(3):211-7 PMID: 20866
- 6. Fukui T et al.. 1987. Purification and characterization of NADP-linked acetoacetyl-CoA reductase from Zoogloea ramigera I-16-M.. Biochim Biophys Acta 917(3):365-71 PMID: 3542050
- 7. Ploux O et al.. 1988. The NADPH-linked acetoacetyl-CoA reductase from Zoogloea ramigera. Characterization and mechanistic studies of the cloned enzyme over-produced in Escherichia coli.. Eur J Biochem 174(1):177-82 PMID: 3286259
- 8. Prasad MR et al.. 1984. Rat hepatic microsomal acetoacetyl-CoA reductase. A beta-ketoacyl-CoA reductase distinct from the long chain beta-ketoacyl-CoA reductase component of the microsomal fatty acid chain elongation system.. J Biol Chem 259(12):7460-7 PMID: 6376489
