The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
The research target CAT2 in Saccharomyces cerevisiae (strain S288c; ORF YML042W) encodes Cat2p, a carnitine O-acetyltransferase/carnitine acetyltransferase that is dually localized to peroxisomes and mitochondria and catalyzes reversible transfer of acetyl groups between acetyl-CoA and L-carnitine, generating acetylcarnitine as a membrane-permeant carrier of acetyl units. (roermund1999molecularcharacterizationof pages 1-2, swiegers2001carnitine‐dependentmetabolicactivities pages 1-2)
Functionally, Cat2p is the principal enzymatic component of the yeast carnitine shuttle for acetyl-unit transfer between organelles, operating in parallel with a glyoxylate-cycle-mediated route (CIT2-dependent); loss of both systems (e.g., Δcit2 Δcat2) abolishes growth on fatty acids such as oleate. (roermund1999molecularcharacterizationof pages 1-2, swiegers2001carnitine‐dependentmetabolicactivities pages 1-2)
Recent work (2023–2024) continues to use Cat2 as a mechanistic handle for inter-organelle metabolism and for real-world metabolic engineering, including peroxisomal surface display of Cat2 to increase cytosolic acetyl-CoA supply and achieve gram-per-liter terpene titers in engineered yeast. (zhang2024denovoproduction pages 8-10)
Primary yeast studies identify CAT2 as encoding a single gene product that yields both peroxisomal and mitochondrial carnitine acetyltransferase activities (Cat2p) in oleate-grown cells. (roermund1999molecularcharacterizationof pages 5-8, roermund1999molecularcharacterizationof pages 1-2)
A 2024 review of dual targeting also lists CAT2 (YML042W) as “carnitine acetyl-CoA transferase” among proteins that occur in both mitochondria and peroxisomes, consistent with UniProt P32796’s description of a mitochondrial precursor enzyme. (freitag2024mitochondriaperoxisomesand pages 1-3)
A frequent source of confusion is the distinction between:
- CAT2 (YML042W): the enzyme catalyzing acetyl transfer to/from carnitine (Cat2p). (roermund1999molecularcharacterizationof pages 1-2, swiegers2001carnitine‐dependentmetabolicactivities pages 1-2)
- YOR100C / CAC / CRC1: the mitochondrial carrier/translocase involved in acetylcarnitine transport across the inner mitochondrial membrane, identified separately in genetic screens for carnitine-dependent acetyl-unit transport. (roermund1999molecularcharacterizationof pages 1-2, swiegers2001carnitine‐dependentmetabolicactivities pages 2-4)
This report is restricted to the S. cerevisiae CAT2 enzyme as specified.
Carnitine acetyltransferases (CATs) catalyze a reversible acyl-transfer between CoA thioesters and carnitine. In yeast CAT biology, the central reaction is:
acetyl-CoA + L-carnitine ⇄ CoA + acetyl-L-carnitine
This reversibility is explicitly described in yeast: peroxisomal CAT forms acetylcarnitine from acetyl-CoA for transport, and mitochondrial CAT catalyzes the reverse reaction to regenerate acetyl-CoA for the TCA cycle. (swiegers2001carnitine‐dependentmetabolicactivities pages 2-4, swiegers2001carnitine‐dependentmetabolicactivities pages 1-2)
Because acetyl-CoA cannot cross organellar membranes directly, yeast uses a carnitine-dependent shuttle to move acetyl units between compartments. In the canonical peroxisome→mitochondrion direction during fatty-acid growth, intraperoxisomal acetyl-CoA is converted to acetylcarnitine by Cat2p and then transported to mitochondria, where acetyl-CoA is regenerated. (roermund1999molecularcharacterizationof pages 1-2, swiegers2001carnitine‐dependentmetabolicactivities pages 2-4)
Yeast also has a parallel acetyl-unit utilization/transport route via glyoxylate-cycle intermediates (CIT2 pathway), explaining genetic redundancy. (roermund1999molecularcharacterizationof pages 1-2)
Cat2p catalyzes the intraperoxisomal conversion of acetyl-CoA into acetylcarnitine (acetyl transfer to carnitine), enabling acetyl-unit transfer out of peroxisomes. (roermund1999molecularcharacterizationof pages 1-2)
Swiegers et al. (2001) further describe the two-direction model: peroxisomal CAT transfers acetyl groups from acetyl-CoA to carnitine, while mitochondrial CAT catalyzes the reverse reaction to generate acetyl-CoA for the TCA cycle. (swiegers2001carnitine‐dependentmetabolicactivities pages 2-4)
In the evidence retrieved here, yeast Cat2 is consistently discussed as acetyltransferase acting on acetyl-CoA/acetylcarnitine (not long-chain acylcarnitines). Additionally, a yeast-focused review/thesis source notes that in S. cerevisiae “only carnitine acetyl-transferase activity has been described,” and that yeast lacks long-chain carnitine acyltransferase activity. (franken2009carnitinemetabolismand pages 32-36)
Multiple sources describe Cat2p as present in both peroxisomes and mitochondria. (roermund1999molecularcharacterizationof pages 1-2, swiegers2001carnitine‐dependentmetabolicactivities pages 1-2)
A yeast review/thesis summary explains dual targeting as mediated by alternative translation initiation/dual targeting signals: two ATG codons can produce isoforms, one containing an N-terminal mitochondrial targeting signal, while a C-terminal PTS1 (AKL) provides peroxisomal targeting potential. (franken2009carnitinemetabolismand pages 32-36)
A 2024 integrative omics study reports that Cat2 localization is sensitive to tagging: N-terminal fluorescent tags yielded a punctate/peroxisomal pattern, whereas C-terminal tags abolished puncta—consistent with disruption of a C-terminal peroxisomal targeting signal—leading to predominant mitochondrial localization. (kosir2024integrativeomicsreveals pages 4-8)
A 2024 review on dual targeting and organelle tethering proposes that efficient tethering can counteract removal from mitochondria and subsequent peroxisomal targeting for presequence-pathway proteins, affecting Cat2 “to some extent.” (freitag2024mitochondriaperoxisomesand pages 3-4)
During growth on fatty acids (e.g., oleate), β-oxidation in yeast occurs in peroxisomes, creating acetyl-CoA that must be handled/transported. Cat2p functions in the carnitine-dependent pathway for transport of acetyl units to mitochondria. (roermund1999molecularcharacterizationof pages 1-2)
Genetic evidence shows redundancy between the carnitine shuttle and glyoxylate-cycle route:
- cat2Δ alone may not impair growth on oleate in some backgrounds/conditions.
- Δcit2 Δcat2 double mutants fail to grow on oleate, consistent with loss of both acetyl-unit transfer/utilization routes. (roermund1999molecularcharacterizationof pages 1-2, swiegers2001carnitine‐dependentmetabolicactivities pages 1-2)
Swiegers et al. also report that although single deletions can be tolerated, in a cit2-disrupted background, L-carnitine and carnitine acetyltransferases become essential for growth on non-fermentable carbon sources. (swiegers2001carnitine‐dependentmetabolicactivities pages 1-2)
Yeast contains at least three carnitine acetyltransferases involved in the shuttle system:
- CAT2: peroxisomal and mitochondrial (major activity).
- YAT1: described as associated with the outer mitochondrial membrane.
- YAT2 (YER024w): described as cytosolic in review/thesis summaries and contributes substantially under ethanol growth. (franken2009carnitinemetabolismand pages 32-36, swiegers2001carnitine‐dependentmetabolicactivities pages 1-2)
In ethanol-grown cells, YAT2 was reported to account for ~50% of total CAT activity in the conditions tested, indicating condition-dependent sharing of measured CAT activity among family members. (swiegers2001carnitine‐dependentmetabolicactivities pages 7-9, swiegers2001carnitine‐dependentmetabolicactivities pages 2-4)
Cat2p is consistently reported as the dominant CAT activity in yeast:
- ~95% of total carnitine acetyltransferase activity in oleate-grown cells. (roermund1999molecularcharacterizationof pages 1-2)
- >99% of total CAT activity in galactose-grown cells (per Swiegers et al.). (swiegers2001carnitine‐dependentmetabolicactivities pages 1-2)
A literature excerpt reports enzyme activity in density-gradient peak fractions for S. cerevisiae grown on oleate: 82.2 nmol/min/mg (peroxisomal peak) and 122.6 nmol/min/mg (mitochondrial peak). (strijbisUnknownyeartheroleof pages 56-58, strijbisUnknownyeartheroleofa pages 56-58)
Note: the same excerpt contains an internal inconsistency (“five times more” in mitochondria) not supported by the provided numeric values; therefore, the numeric values are reported directly and should be interpreted cautiously without the original figure. (strijbisUnknownyeartheroleof pages 56-58)
A 2024 review positions Cat2 among dually targeted proteins whose steady-state distribution can be influenced by organelle tethering/contact-site mechanisms, providing an updated conceptual framework for how a protein like Cat2 can populate both mitochondria and peroxisomes. (freitag2024mitochondriaperoxisomesand pages 3-4)
Kosir et al. (bioRxiv, March 2024) provide a modern, high-throughput context (matched proteomics + transcriptomics) and an experimental caution: Cat2’s observed peroxisomal localization can be lost with C-terminal tags (consistent with PTS1 disruption), which is directly relevant to functional annotation pipelines that use tagged libraries. (kosir2024integrativeomicsreveals pages 4-8)
Zhang et al. (Microbial Cell Factories, May 2024) explicitly leverage Cat2 enzymology and bidirectionality: they anchor Cat2 to the peroxisome surface (via a Pex15 C-terminal anchor) to facilitate direct cytosolic conversion of acetylcarnitine into acetyl-CoA, improving precursor supply for sesterterpenoid biosynthesis. (zhang2024denovoproduction pages 8-10)
Quantitative engineering outcomes reported include intermediate and final production metrics (see Applications). (zhang2024denovoproduction pages 8-10)
Use case: High-titer production of sesterterpenoid ophiobolins requires large acetyl-CoA supply.
Implementation: Zhang et al. (2024) describe that Cat2 transfers acetyl groups to carnitine forming acetylcarnitine, which can be shuttled across membranes; by exploiting bidirectionality, they position Cat2 on the peroxisome surface to convert acetylcarnitine into cytosolic acetyl-CoA (Fig. 2E in their paper). (zhang2024denovoproduction pages 8-10)
Reported titers/statistics:
- 178 mg/L ophiobolin F (OphF) on oleic acid substrate in one condition.
- 649.6 mg/L OphF with tPOS5 overexpression.
- 742.3 mg/L OphF in strain Yoph19 (reported as a 14% increase vs comparator).
- 5.1 g/L OphF after 72 h in fed-batch whole-cell transformation with intermittent addition of 75 g/L ethanol and 20 g/L oleic acid, in the Cat2 peroxisomal-surface strain (Yoph20). (zhang2024denovoproduction pages 8-10)
This is an example of Cat2 being used as an engineered metabolic “valve” connecting peroxisomal β-oxidation-derived acetyl units to cytosolic acetyl-CoA-demanding biosynthetic pathways. (zhang2024denovoproduction pages 8-10)
The following table summarizes the main supported claims, quantitative values, and metadata.
| Category | Specific finding | Key quantitative data (if any) | Source (first author year) | Publication date (month/year if known) | URL/DOI |
|---|---|---|---|---|---|
| Identity | CAT2 (YML042W) in S. cerevisiae encodes Cat2p, the major carnitine acetyltransferase/carnitine O-acetyltransferase in yeast; literature distinguishes it from the mitochondrial carnitine carrier gene (YOR100C/CAC/CRC1). (roermund1999molecularcharacterizationof pages 1-2, roermund1999molecularcharacterizationof pages 5-8, freitag2024mitochondriaperoxisomesand pages 1-3) | Major CAT enzyme in yeast | van Roermund 1999; Freitag 2024 | Nov 1999; Jan 2024 | https://doi.org/10.1093/emboj/18.21.5843 ; https://doi.org/10.1177/25152564241264254 |
| Reaction | Cat2p catalyzes reversible transfer of acetyl groups between acetyl-CoA and L-carnitine, i.e. acetyl-CoA + carnitine ⇄ CoA + acetylcarnitine; in the peroxisome it forms acetylcarnitine, and in mitochondria the reverse reaction regenerates acetyl-CoA for the TCA cycle. (swiegers2001carnitine‐dependentmetabolicactivities pages 1-2, roermund1999molecularcharacterizationof pages 1-2, swiegers2001carnitine‐dependentmetabolicactivities pages 2-4) | Reversible acetyl transfer; no kinetic constants retrieved in context | Swiegers 2001; van Roermund 1999 | May 2001; Nov 1999 | https://doi.org/10.1002/yea.712 ; https://doi.org/10.1093/emboj/18.21.5843 |
| Localization | Cat2p is dually localized to peroxisomes and mitochondria; review and thesis evidence describe dual targeting mediated by N-terminal mitochondrial targeting information plus a C-terminal peroxisomal targeting signal, with two ATG codons contributing to alternative targeting. (franken2009carnitinemetabolismand pages 32-36, roermund1999molecularcharacterizationof pages 1-2, freitag2024mitochondriaperoxisomesand pages 1-3) | Dual organellar localization | van Roermund 1999; Franken 2009; Freitag 2024 | Nov 1999; 2009; Jan 2024 | https://doi.org/10.1093/emboj/18.21.5843 ; https://doi.org/10.1177/25152564241264254 |
| Pathway role | Cat2p is central to the carnitine shuttle that moves acetyl units from peroxisomes to mitochondria when acetyl-CoA itself cannot cross membranes; this pathway complements the glyoxylate-cycle route for acetyl-unit utilization. (roermund1999molecularcharacterizationof pages 1-2, swiegers2001carnitine‐dependentmetabolicactivities pages 1-2) | Functions in one of two parallel acetyl-unit transport routes | van Roermund 1999; Swiegers 2001 | Nov 1999; May 2001 | https://doi.org/10.1093/emboj/18.21.5843 ; https://doi.org/10.1002/yea.712 |
| Genetics & phenotypes | cat2Δ single mutants can grow similarly to wild type on tested carbon sources, but Δcit2 Δcat2 double mutants fail on oleate/non-fermentable carbon sources, showing redundancy between Cat2-mediated shuttle and the glyoxylate-cycle pathway. (swiegers2001carnitine‐dependentmetabolicactivities pages 7-9, swiegers2001carnitine‐dependentmetabolicactivities pages 5-7, roermund1999molecularcharacterizationof pages 1-2) | Double-mutant synthetic growth defect/loss on oleate and related conditions | van Roermund 1999; Swiegers 2001 | Nov 1999; May 2001 | https://doi.org/10.1093/emboj/18.21.5843 ; https://doi.org/10.1002/yea.712 |
| Genetics & phenotypes | All three yeast carnitine acetyltransferases—CAT2, YAT1, YAT2—are required for a fully functional carnitine shuttle in a cit2-disrupted background, and they do not cross-complement, implying distinct subcellular roles. (franken2009carnitinemetabolismand pages 32-36, swiegers2001carnitine‐dependentmetabolicactivities pages 2-4) | YAT2 contributes ~50% of total CAT activity on ethanol; no cross-complementation | Swiegers 2001; Franken 2009 | May 2001; 2009 | https://doi.org/10.1002/yea.712 |
| Quantitative activity | Cat2p provides the majority of total carnitine acetyltransferase activity in yeast. Reported contributions vary with growth condition: ~95% in oleate-grown cells, >99% in galactose-grown cells, and ~95% overall dominance in review/thesis summaries. (swiegers2001carnitine‐dependentmetabolicactivities pages 1-2, roermund1999molecularcharacterizationof pages 1-2) | ~95% (oleate); >99% (galactose) | van Roermund 1999; Swiegers 2001 | Nov 1999; May 2001 | https://doi.org/10.1093/emboj/18.21.5843 ; https://doi.org/10.1002/yea.712 |
| Quantitative activity | Fractionation/enzyme-assay excerpts report bimodal Cat activity in S. cerevisiae organelle fractions, with 82.2 nmol/min/mg in the peroxisomal peak and 122.6 nmol/min/mg in the mitochondrial peak; the same source states CAT2 contributes about 95% of total activity in oleate-grown cells. (strijbisUnknownyeartheroleof pages 56-58, strijbisUnknownyeartheroleofa pages 56-58) | 82.2 vs 122.6 nmol/min/mg; ~95% of total activity | Strijbis et al. unknown year excerpt | Unknown | URL not available in gathered context |
| Recent 2023-2024 developments | A 2024 review places Cat2 among dually targeted mitochondria/peroxisome proteins and notes that organelle tethering can influence whether such proteins remain mitochondrial or proceed to peroxisomes, affecting Cat2 “to some extent.” (freitag2024mitochondriaperoxisomesand pages 3-4) | No Cat2-specific numeric values reported | Freitag 2024 | Jan 2024 | https://doi.org/10.1177/25152564241264254 |
| Recent 2023-2024 developments | In acetate-grown cells, Cat2 with an N-terminal fluorescent tag showed punctate/peroxisomal localization, whereas C-terminal tagging disrupted the PTS1-dependent punctate pattern, yielding predominant mitochondrial localization; this supports dual targeting and sensitivity of Cat2 localization to tag placement. (kosir2024integrativeomicsreveals pages 4-8) | Proteomics/transcriptomics used 3 biological replicates; analysis thresholds ≥1.5 or ≤0.66 fold, p=0.05, but no Cat2-specific fold-change given | Kosir 2024 | Mar 2024 | https://doi.org/10.1101/2024.03.20.585854 |
| Applications & engineering | Cat2 has been repurposed in metabolic engineering: anchoring Cat2 to the peroxisome surface was used to channel acetyl units from peroxisomal β-oxidation toward the cytosolic acetyl-CoA pool for ophiobolin biosynthesis; authors explicitly exploit the bidirectionality of Cat2 catalysis. (zhang2024denovoproduction pages 8-10) | Surface-localized Cat2 strain (Yoph20) reached 5.1 g/L ophiobolin F after 72 h fed-batch whole-cell transformation; other reported titers include 178 mg/L, 649.6 mg/L, and 742.3 mg/L OphF in intermediate strains/conditions | Zhang 2024 | May 2024 | https://doi.org/10.1186/s12934-024-02406-0 |
Table: This table summarizes verified findings on S. cerevisiae CAT2/Cat2p, covering identity, biochemical function, localization, pathway context, genetics, quantitative activity, and recent 2023-2024 developments. It is useful as a compact evidence map linking classic yeast genetics with current organelle biology and metabolic engineering work.
References
(roermund1999molecularcharacterizationof pages 1-2): C. V. van Roermund, E. Hettema, M. van den Berg, H. Tabak, and R. Wanders. Molecular characterization of carnitine‐dependent transport of acetyl‐coa from peroxisomes to mitochondria in saccharomyces cerevisiae and identification of a plasma membrane carnitine transporter, agp2p. The EMBO Journal, 18:5843-5852, Nov 1999. URL: https://doi.org/10.1093/emboj/18.21.5843, doi:10.1093/emboj/18.21.5843. This article has 249 citations.
(swiegers2001carnitine‐dependentmetabolicactivities pages 1-2): Jan H. Swiegers, Nola Dippenaar, Isak S. Pretorius, and Florian F. Bauer. Carnitine‐dependent metabolic activities in saccharomyces cerevisiae: three carnitine acetyltransferases are essential in a carnitine‐dependent strain. Yeast, 18:585-595, May 2001. URL: https://doi.org/10.1002/yea.712, doi:10.1002/yea.712. This article has 130 citations and is from a peer-reviewed journal.
(zhang2024denovoproduction pages 8-10): Caizhe Zhang, Jun Wu, Qing Sun, Shuaishuai Ding, Hua Tao, Yuhua He, Hui Qiu, Bei Shu, Dongqing Zhu, Hengcheng Zhu, and Kui Hong. De novo production of bioactive sesterterpenoid ophiobolins in saccharomyces cerevisiae cell factories. Microbial Cell Factories, May 2024. URL: https://doi.org/10.1186/s12934-024-02406-0, doi:10.1186/s12934-024-02406-0. This article has 11 citations and is from a peer-reviewed journal.
(roermund1999molecularcharacterizationof pages 5-8): C. V. van Roermund, E. Hettema, M. van den Berg, H. Tabak, and R. Wanders. Molecular characterization of carnitine‐dependent transport of acetyl‐coa from peroxisomes to mitochondria in saccharomyces cerevisiae and identification of a plasma membrane carnitine transporter, agp2p. The EMBO Journal, 18:5843-5852, Nov 1999. URL: https://doi.org/10.1093/emboj/18.21.5843, doi:10.1093/emboj/18.21.5843. This article has 249 citations.
(freitag2024mitochondriaperoxisomesand pages 1-3): Johannes Freitag, Thorsten Stehlik, and Gert Bange. Mitochondria, peroxisomes and beyond—how dual targeting regulates organelle tethering. Contact, Jan 2024. URL: https://doi.org/10.1177/25152564241264254, doi:10.1177/25152564241264254. This article has 1 citations.
(swiegers2001carnitine‐dependentmetabolicactivities pages 2-4): Jan H. Swiegers, Nola Dippenaar, Isak S. Pretorius, and Florian F. Bauer. Carnitine‐dependent metabolic activities in saccharomyces cerevisiae: three carnitine acetyltransferases are essential in a carnitine‐dependent strain. Yeast, 18:585-595, May 2001. URL: https://doi.org/10.1002/yea.712, doi:10.1002/yea.712. This article has 130 citations and is from a peer-reviewed journal.
(franken2009carnitinemetabolismand pages 32-36): J Franken. Carnitine metabolism and biosynthesis in the yeast saccharomyces cerevisiae. Unknown journal, 2009.
(kosir2024integrativeomicsreveals pages 4-8): Tjasa Kosir, Hirak Das, Marc Pilegaard Pedersen, Marco Anteghini, Silke Oeljeklaus, Vitor Martins dos Santos, Ida J. van der Klei, and Bettina Warscheid. Integrative omics reveals changes in the cellular landscape of yeast without peroxisomes. bioRxiv, Mar 2024. URL: https://doi.org/10.1101/2024.03.20.585854, doi:10.1101/2024.03.20.585854. This article has 3 citations.
(freitag2024mitochondriaperoxisomesand pages 3-4): Johannes Freitag, Thorsten Stehlik, and Gert Bange. Mitochondria, peroxisomes and beyond—how dual targeting regulates organelle tethering. Contact, Jan 2024. URL: https://doi.org/10.1177/25152564241264254, doi:10.1177/25152564241264254. This article has 1 citations.
(swiegers2001carnitine‐dependentmetabolicactivities pages 7-9): Jan H. Swiegers, Nola Dippenaar, Isak S. Pretorius, and Florian F. Bauer. Carnitine‐dependent metabolic activities in saccharomyces cerevisiae: three carnitine acetyltransferases are essential in a carnitine‐dependent strain. Yeast, 18:585-595, May 2001. URL: https://doi.org/10.1002/yea.712, doi:10.1002/yea.712. This article has 130 citations and is from a peer-reviewed journal.
(strijbisUnknownyeartheroleof pages 56-58): K Strijbis, C van Roermund, and M van de Berg. The role of candida albicans peroxisomal and mitochondrial carnitine acetyl-tranferases in intracellular acetyl unit transport. Unknown journal, Unknown year.
(strijbisUnknownyeartheroleofa pages 56-58): K Strijbis, C van Roermund, and M van de Berg. The role of candida albicans peroxisomal and mitochondrial carnitine acetyl-tranferases in intracellular acetyl unit transport. Unknown journal, Unknown year.
(swiegers2001carnitine‐dependentmetabolicactivities pages 5-7): Jan H. Swiegers, Nola Dippenaar, Isak S. Pretorius, and Florian F. Bauer. Carnitine‐dependent metabolic activities in saccharomyces cerevisiae: three carnitine acetyltransferases are essential in a carnitine‐dependent strain. Yeast, 18:585-595, May 2001. URL: https://doi.org/10.1002/yea.712, doi:10.1002/yea.712. This article has 130 citations and is from a peer-reviewed journal.