Ald4p is the major mitochondrial aldehyde dehydrogenase of S. cerevisiae (the K+-activated acetaldehyde dehydrogenase, EC 1.2.1.5), a matrix enzyme imported via an N-terminal presequence. It oxidizes acetaldehyde and other short aliphatic aldehydes to the corresponding carboxylates using either NAD+ or NADP+, with a low micromolar Km for acetaldehyde. ALD4 is glucose-repressed and Ald4p is needed for efficient growth on ethanol, where it oxidizes ethanol-derived acetaldehyde to acetate in mitochondria. During glucose fermentation it backs up the cytosolic Ald6p in acetate formation (ALD4 is induced when Ald6p is absent and ald4 ald6 double mutants are severely delayed). Its NADP+-linked activity also makes Ald4p a major source of mitochondrial NADPH, acting downstream of the Pos5 NAD(H) kinase. During meiosis Ald4p polymerizes into filaments inside mitochondria, identified by cryo-electron tomography of sporulating cells.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004029 aldehyde dehydrogenase (NAD+) activity | IBA GO_REF:0000033 | ACCEPT | Summary: IBA aldehyde dehydrogenase (NAD+) activity from the broad ALDH1/ALDH2 class node PTN000192666 (mammalian ALDH1A/ALDH2, E. coli, Drosophila and yeast ALD4/ALD5 donors). Reason: Ald4p sits within this NAD-using class-1/2 ALDH clade, and NAD+-linked aldehyde oxidation by Ald4p is directly supported (the enzyme uses NAD or NADP, Vmax about twofold higher with NAD). The inferred activity is correct for the target. Supporting Evidence: PMID:9473035 Like ALDH5, the commercial ALDH2 enzyme used either NAD or NADP as a cofactor. file:yeast/ALD4/ALD4-uniprot.txt Reaction=an aldehyde + NAD(+) + H2O = a carboxylate + NADH + 2 H(+); |
| GO:0004029 aldehyde dehydrogenase (NAD+) activity | IDA PMID:9473035 Molecular cloning, characterization, and potential roles of ... | ACCEPT | Summary: IDA from Wang et al. 1998, who assayed the commercial yeast mitochondrial K+-activated ALDH (their ALDH2, chromosome XV = ALD4/YOR374W) with NAD+ and NADP+. Reason: Wang et al. name this enzyme ALDH2; their chromosome XV assignment and partial sequence identify it as the ALD4 product. They show it uses either NAD or NADP. Correct. Supporting Evidence: PMID:9473035 The commercial ALDH (designated ALDH2) was partially sequenced and appears to be a mitochondrial enzyme encoded by a gene located on chromosome XV. PMID:9473035 Like ALDH5, the commercial ALDH2 enzyme used either NAD or NADP as a cofactor. |
| GO:0004029 aldehyde dehydrogenase (NAD+) activity | IEA GO_REF:0000116 | ACCEPT | Summary: IEA from Rhea mapping (RHEA:16185, RHEA:67256 propanal + NAD+) in the UniProt entry. Reason: Reflects the experimentally recorded NAD+-dependent activity of Ald4p (UniProt, from PMID:9473035); correct. Supporting Evidence: file:yeast/ALD4/ALD4-uniprot.txt Reaction=an aldehyde + NAD(+) + H2O = a carboxylate + NADH + 2 H(+); |
| GO:0004029 aldehyde dehydrogenase (NAD+) activity | IMP PMID:9675847 Identification and disruption of the gene encoding the K(+)-... | ACCEPT | Summary: IMP from Tessier et al. 1998: deletion of YOR374w (named ALD7 there, now ALD4) abolishes the mitochondrial K+-activated acetaldehyde dehydrogenase activity. Reason: Loss of the K+-ACDH activity in the deletion mutant ties the NAD(P)+-linked mitochondrial ALDH activity to this gene. The paper uses the obsolete name ALD7 for YOR374w; the gene identity is unambiguous. Supporting Evidence: PMID:9675847 The gene is situated on the right arm of chromosome XV, bears the systematic name YOR374w PMID:9675847 Haploid mutants containing a deletion of ALD7 were constructed and, in these strains, the K(+)-ACDH was not detectable under any growth conditions examined. |
| GO:0004030 aldehyde dehydrogenase [NAD(P)+] activity | IDA PMID:9473035 Molecular cloning, characterization, and potential roles of ... | ACCEPT | Summary: IDA aldehyde dehydrogenase [NAD(P)+] activity from Wang et al. 1998. Reason: Ald4p is a dual-cofactor (NAD+ or NADP+) mitochondrial ALDH; this grouping term exactly captures that property and is used as the core MF. Supporting Evidence: PMID:9473035 Like ALDH5, the commercial ALDH2 enzyme used either NAD or NADP as a cofactor. |
| GO:0004030 aldehyde dehydrogenase [NAD(P)+] activity | IEA GO_REF:0000003 | ACCEPT | Summary: IEA from EC 1.2.1.5 (aldehyde dehydrogenase [NAD(P)+]) mapping. Reason: UniProt assigns EC 1.2.1.5 to Ald4p based on Wang et al.; correct and consistent with its dual cofactor use. Supporting Evidence: file:yeast/ALD4/ALD4-uniprot.txt Reaction=an aldehyde + NADP(+) + H2O = a carboxylate + NADPH + 2 H(+); |
| GO:0004030 aldehyde dehydrogenase [NAD(P)+] activity | RCA GO_REF:0000123 | ACCEPT | Summary: RCA from YeastPathways superpathway of glucose fermentation (acetaldehyde + NAD(P)+ -> acetate). Reason: The MF is correct for Ald4p. The fermentation-context is partly supported: Ald4p compensates for loss of Ald6p (ALD4 is transcriptionally activated in ald6 mutants) and contributes modestly to acetate formation in some strains. Supporting Evidence: PMID:15256563 The absence of Ald6p was compensated by the mitochondrial isoforms and this involves the transcriptional activation of ALD4. PMID:10919763 In contrast, a strain lacking both Ald6p and Ald4p exhibited a long delay in growth and acetate production, suggesting that Ald4p can partially replace the Ald6p isoform. |
| GO:0005739 mitochondrion | HDA PMID:14576278 The proteome of Saccharomyces cerevisiae mitochondria. | ACCEPT | Summary: HDA from the Sickmann et al. 2003 mitochondrial proteome. Reason: Ald4p is a well-established mitochondrial (matrix) enzyme; proteomic detection agrees. Supporting Evidence: PMID:14576278 The proteins of highly pure yeast mitochondria were separated by several independent methods and analyzed by tandem MS. file:yeast/ALD4/ALD4-uniprot.txt SUBCELLULAR LOCATION: Mitochondrion matrix |
| GO:0005739 mitochondrion | HDA PMID:16823961 Toward the complete yeast mitochondrial proteome: multidimen... | ACCEPT | Summary: HDA from Reinders et al. 2006 mitochondrial proteome. Reason: Consistent with the established mitochondrial matrix location. Supporting Evidence: PMID:16823961 Proteomic analyses of different subcellular compartments, so-called organellar proteomics |
| GO:0005739 mitochondrion | HDA PMID:24769239 Quantitative variations of the mitochondrial proteome and ph... | ACCEPT | Summary: HDA from Renvoise et al. 2014 quantitative mitochondrial proteome (fermentative vs respiratory). Reason: Consistent with the established mitochondrial matrix location. Supporting Evidence: PMID:24769239 Quantitative variations of the mitochondrial proteome and phosphoproteome during fermentative and respiratory growth in Saccharomyces cerevisiae |
| GO:0005739 mitochondrion | IBA GO_REF:0000033 | ACCEPT | Summary: IBA is_active_in mitochondrion from PTN000916385, seeded by the yeast ALD4/ALD5/ALD6 annotations. Reason: Correct for Ald4p, which carries an N-terminal mitochondrial presequence and acts in the matrix. (The same node propagates a less appropriate is_active_in mitochondrion to cytosolic Ald6p; see the ALD6 review.) Supporting Evidence: PMID:9473035 The commercial ALDH (designated ALDH2) was partially sequenced and appears to be a mitochondrial enzyme encoded by a gene located on chromosome XV. file:yeast/ALD4/ALD4-uniprot.txt SUBCELLULAR LOCATION: Mitochondrion matrix |
| GO:0005739 mitochondrion | IDA PMID:11502169 Yeast mitochondrial dehydrogenases are associated in a supra... | ACCEPT | Summary: IDA from Grandier-Vazeille et al. 2001: Ald4p identified in a mitochondrial supramolecular dehydrogenase complex separated by native PAGE. Reason: Direct biochemical identification in purified mitochondria; supports mitochondrial location (UniProt cites this paper for matrix localization). Supporting Evidence: PMID:11502169 and the acetaldehyde dehydrogenase Ald4p |
| GO:0005759 mitochondrial matrix | IEA GO_REF:0000120 | ACCEPT | Summary: IEA mitochondrial matrix from ARBA / UniProt SubCell SL-0170. Reason: Correct; Ald4p is a soluble matrix ALDH. Core location. Supporting Evidence: file:yeast/ALD4/ALD4-uniprot.txt SUBCELLULAR LOCATION: Mitochondrion matrix |
| GO:0005829 cytosol | RCA GO_REF:0000123 | REMOVE | Summary: RCA is_active_in cytosol from YeastPathways superpathway of glucose fermentation. Reason: The pathway-to-GO conversion assigns the cytosolic compartment of the PDH-bypass reaction to every enzyme attached to it. Ald4p is a mitochondrial matrix enzyme with an N-terminal presequence and is not active in the cytosol; this compartment assertion is contradicted by the experimental localization evidence. Supporting Evidence: file:yeast/ALD4/ALD4-uniprot.txt SUBCELLULAR LOCATION: Mitochondrion matrix PMID:9473035 The commercial ALDH (designated ALDH2) was partially sequenced and appears to be a mitochondrial enzyme encoded by a gene located on chromosome XV. |
| GO:0006067 ethanol metabolic process | IMP PMID:9675847 Identification and disruption of the gene encoding the K(+)-... | ACCEPT | Summary: IMP ethanol metabolic process from Tessier et al. 1998: ald4 (ALD7) deletion severely impairs growth on ethanol. Reason: Ald4p is the major mitochondrial acetaldehyde dehydrogenase used during growth on ethanol; the mutant phenotype directly supports its role in ethanol oxidation. The more specific ethanol catabolic process (GO:0006068) is used as core process. Supporting Evidence: PMID:9675847 Growth on glucose was not affected in the mutants lacking ALD7 (in contrast to the behaviour of ald6 mutants), whereas growth on ethanol was severely impaired. |
| GO:0006629 lipid metabolic process | IMP PMID:39462103 Regulating the metabolic flux of pyruvate dehydrogenase bypa... | MARK AS OVER ANNOTATED | Summary: IMP acts_upstream_of_or_within lipid metabolic process from Lei et al. 2024: ALD4 overexpression increased total lipid content by about 20%. Reason: This is an overexpression/metabolic-engineering phenotype: extra Ald4p alters acetaldehyde/acetate flux and hence acetyl-CoA supply, which indirectly raises lipid accumulation. Ald4p does not perform any step of lipid metabolism; the effect is indirect and pleiotropic. Supporting Evidence: PMID:39462103 Genetic validation demonstrated that overexpression of the mitochondrial acetaldehyde dehydrogenase (ALDH) gene ALD4 resulted in a 20.1% increase in lipid production. |
| GO:0006740 NADPH regeneration | IGI PMID:19158096 Two sources of mitochondrial NADPH in the yeast Saccharomyce... | ACCEPT | Summary: IGI NADPH regeneration from Miyagi et al. 2009 (genetic interaction with POS5). Reason: Ald4p reduces NADP+ to NADPH while oxidizing acetaldehyde in the matrix and is shown to be a main source of mitochondrial NADPH when the Pos5 NADH-kinase reaction is absent. Ald4p directly performs the NADPH-producing step, so this is a genuine (secondary) process role. Supporting Evidence: PMID:19158096 evidence is presented that acetaldehyde dehydrogenases, and in particular Ald4p, play a prominent role in generating mitochondrial NADPH in the absence of the NADH kinase reaction. |
| GO:0016491 oxidoreductase activity | IEA GO_REF:0000002 | TOO GENERAL | Summary: InterPro2GO IEA generic oxidoreductase activity. Reason: Correct but uninformative; specific ALDH terms are present. |
| GO:0019413 acetate biosynthetic process | IEA GO_REF:0000117 | ACCEPT | Summary: ARBA IEA acetate biosynthetic process. Reason: Ald4p oxidizes acetaldehyde to acetate; consistent with the IGI evidence and with UniProt's function statement. Supporting Evidence: file:yeast/ALD4/ALD4-uniprot.txt FUNCTION: Potassium-activated aldehyde dehydrogenase involved in PMID:10919763 In contrast, a strain lacking both Ald6p and Ald4p exhibited a long delay in growth and acetate production, suggesting that Ald4p can partially replace the Ald6p isoform. |
| GO:0019413 acetate biosynthetic process | IGI PMID:10919763 Engineering of the pyruvate dehydrogenase bypass in Saccharo... | ACCEPT | Summary: IGI acetate biosynthetic process from Remize et al. 2000 (with ALD6). Reason: Single ald4 deletion has no effect on acetate, but ald4 ald6 double mutants show delayed acetate production, indicating Ald4p can partially replace Ald6p in forming acetate. Supports Ald4p performing the acetaldehyde -> acetate step. Supporting Evidence: PMID:10919763 K(+)-activated NAD(P)-linked ACDH, had no effect on the amount of acetate PMID:10919763 In contrast, a strain lacking both Ald6p and Ald4p exhibited a long delay in growth and acetate production, suggesting that Ald4p can partially replace the Ald6p isoform. |
| GO:0019658 bifid shunt | RCA GO_REF:0000123 | REMOVE | Summary: RCA bifid shunt from YeastPathways superpathway of glucose fermentation. Reason: GO:0019658 describes the bifidobacterial phosphoketolase pathway (glucose -> lactate + acetate); S. cerevisiae has no bifid shunt. This is a superpathway-mapping artefact; the relevant processes for Ald4p are ethanol catabolism and acetate biosynthesis. |
| GO:0033721 aldehyde dehydrogenase (NADP+) activity | EXP PMID:9473035 Molecular cloning, characterization, and potential roles of ... | ACCEPT | Summary: EXP aldehyde dehydrogenase (NADP+) activity from Wang et al. 1998. Reason: Ald4p (Wang's ALDH2) uses NADP+ as well as NAD+; correct, and consistent with its role in mitochondrial NADPH production. Supporting Evidence: PMID:9473035 Like ALDH5, the commercial ALDH2 enzyme used either NAD or NADP as a cofactor. file:yeast/ALD4/ALD4-uniprot.txt Reaction=an aldehyde + NADP(+) + H2O = a carboxylate + NADPH + 2 H(+); |
| GO:0033721 aldehyde dehydrogenase (NADP+) activity | IEA GO_REF:0000116 | ACCEPT | Summary: IEA from Rhea mapping (RHEA:11888, RHEA:27918). Reason: Matches the experimentally recorded NADP+-linked activity; correct. Supporting Evidence: file:yeast/ALD4/ALD4-uniprot.txt Reaction=an aldehyde + NADP(+) + H2O = a carboxylate + NADPH + 2 H(+); |
| GO:0033721 aldehyde dehydrogenase (NADP+) activity | RCA GO_REF:0000123 | ACCEPT | Summary: RCA from YeastPathways superpathway of glucose fermentation (EC 1.2.1.4 aldehyde + NADP+). Reason: MF correct for Ald4p, independent of the superpathway context. Supporting Evidence: file:yeast/ALD4/ALD4-uniprot.txt Reaction=an aldehyde + NADP(+) + H2O = a carboxylate + NADPH + 2 H(+); |
| GO:0042645 mitochondrial nucleoid | IDA PMID:10869431 In organello formaldehyde crosslinking of proteins to mtDNA:... | KEEP AS NON CORE | Summary: IDA mitochondrial nucleoid from Kaufman et al. 2000, an in organello formaldehyde cross-linking screen for mtDNA-associated proteins. Reason: The cached abstract does not name Ald4p, so the specific evidence cannot be checked here; the curator presumably saw Ald4p among the cross-linked proteins in the full text. Crosslinking of an abundant matrix enzyme to mtDNA is plausible but no nucleoid function has been described for Ald4p; keep as a non-core location. Supporting Evidence: PMID:10869431 We detected approximately 20 proteins crosslinked to mtDNA and identified 11, mostly by mass spectrometry. |
| GO:0140088 acetaldehyde dehydrogenase (NADP+) activity | EXP PMID:9473035 Molecular cloning, characterization, and potential roles of ... | ACCEPT | Summary: EXP acetaldehyde dehydrogenase (NADP+) activity from Wang et al. 1998. Reason: UniProt lists acetaldehyde + NADP+ -> acetate with kinetic parameters for Ald4p (Km acetaldehyde 10 uM) from this paper. Specific physiological activity in ethanol oxidation and mitochondrial NADPH supply. Supporting Evidence: file:yeast/ALD4/ALD4-uniprot.txt Reaction=acetaldehyde + NADP(+) + H2O = acetate + NADPH + 2 H(+); PMID:9473035 Like ALDH5, the commercial ALDH2 enzyme used either NAD or NADP as a cofactor. |
| GO:0140088 acetaldehyde dehydrogenase (NADP+) activity | IEA GO_REF:0000120 | ACCEPT | Summary: IEA (ARBA / RHEA:25298) acetaldehyde dehydrogenase (NADP+) activity. Reason: Correct, matches experimentally recorded activity. Supporting Evidence: file:yeast/ALD4/ALD4-uniprot.txt Reaction=acetaldehyde + NADP(+) + H2O = acetate + NADPH + 2 H(+); |
| GO:0006068 ethanol catabolic process | IMP PMID:9675847 Identification and disruption of the gene encoding the K(+)-... | NEW | Summary: Proposed involved_in ethanol catabolic process for Ald4p, refining the existing IMP ethanol metabolic process row. Reason: Ald4p itself catalyzes the acetaldehyde -> acetate step of ethanol oxidative degradation in mitochondria; ald4 deletion abolishes the K+-ACDH activity and severely impairs growth on ethanol. This is participation (the enzyme performs a step), and the paralog Ald6p/Ald5p already carry this term via UniPathway mapping. The more specific catabolic child is more informative than GO:0006067. Supporting Evidence: PMID:9675847 Haploid mutants containing a deletion of ALD7 were constructed and, in these strains, the K(+)-ACDH was not detectable under any growth conditions examined. PMID:9675847 Growth on glucose was not affected in the mutants lacking ALD7 (in contrast to the behaviour of ald6 mutants), whereas growth on ethanol was severely impaired. |
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Download this section (compressed HTML)Q: Which aldehydes other than acetaldehyde are physiological Ald4p substrates in the matrix (e.g. propanal, branched-chain aldehydes from amino acid catabolism, furfural)?
Q: Is the reported association of Ald4p with mtDNA nucleoids functionally meaningful or incidental crosslinking of an abundant matrix protein?
Experiment: Measure matrix NADPH/NADP+ ratios with a compartment-targeted sensor in ald4, pos5 and ald4 pos5 strains on ethanol to quantify the contribution of Ald4p to mitochondrial NADPH.
Mitochondrial aldehyde dehydrogenase; K+ dependent enzyme that can use either NADP+ or NAD+ as cofactor; required for growth on ethanol and for conversion of acetaldehyde to acetate; can substitute for cytosolic NADP-dependent aldehyde dehydrogenase when directed to the cytosol; influences lipid metabolism; polymerizes into filaments in meiotic cells; phosphorylated; expression is glucose repressed; human homolog ALDH2 can complement a yeast ald4 mutant
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