Ald6p is the constitutive, cytosolic, Mg2+-activated aldehyde dehydrogenase of S. cerevisiae and the most abundant ALD family member. It is essentially NADP+-specific (Km for NAD+ about 170-fold higher than for NADP+) and oxidizes acetaldehyde, propanal and related short aldehydes. As the acetaldehyde dehydrogenase of the cytosolic pyruvate dehydrogenase bypass, Ald6p generates most of the acetate formed during glucose fermentation, which is activated to cytosolic acetyl-CoA by acetyl-CoA synthetase; ald6 mutants grow slowly on glucose, produce much less acetate and cannot grow on ethanol. Because it reduces NADP+, Ald6p is also a major source of cytosolic NADPH, acting redundantly with glucose-6-phosphate dehydrogenase (zwf1 ald6 double mutants are inviable). Loss of ALD6 also alters tolerance to salt stress under calcineurin inhibition. Ald6p is itself a preferred substrate of autophagic degradation during nitrogen starvation, and ald6 deletion enhances starvation-induced autophagy, so this NADPH-generating enzyme, a direct transcriptional target of Stb5, acts as a negative regulator of nonselective autophagy.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004029 aldehyde dehydrogenase (NAD+) activity | IBA GO_REF:0000033 | MARK AS OVER ANNOTATED | Summary: IBA aldehyde dehydrogenase (NAD+) activity from the broad class-1/2 ALDH node PTN000192666, whose donors are mostly NAD+-dependent mammalian/bacterial ALDHs and yeast ALD4/ALD5. Reason: Ald6p diverges from the NAD-preferring members of this node: Wang et al. show the Km for NAD+ is 170-fold higher than for NADP+ (17.4 mM with propanal), and conclude the enzyme is essentially NADP-dependent. NAD+-linked turnover is measurable in vitro only at non-physiological cofactor concentrations, so the inherited NAD+-specific term over-states this activity; the NADP+-specific terms describe Ald6p. Propagation Review Root cause: PROPAGATION BAD Failure modes: FUNCTIONAL DIVERGENCE Sources checked: PANTHER:PTN000192666 · PTN000192666 SUPPORTS SOURCE BUT NOT TARGET NAD+-preferring class-1/2 ALDH node; Ald6p has diverged to NADP+ specificity (170-fold higher Km for NAD+). Supporting Evidence: PMID:9473035 The K m value for NAD with ALDH1 was 170-fold higher than that of NADP even though the V max value differed by a factor of only 2 (Table 3 ). Thus, we have concluded that ALDH1 is essentially an NADP-dependent enzyme. file:yeast/ALD6/ALD6-uniprot.txt KM=17.4 mM for NAD (with propanal as cosubstrate) |
| GO:0004030 aldehyde dehydrogenase [NAD(P)+] activity | IDA PMID:9473035 Molecular cloning, characterization, and potential roles of ... | TOO GENERAL | Summary: IDA aldehyde dehydrogenase [NAD(P)+] activity from Wang et al. 1998 (their ALDH1 = Ald6p, chromosome XVI). Reason: Correct as a grouping term; the more specific NADP+-dependent terms (GO:0033721, GO:0140088) better describe Ald6p and are used as core. Supporting Evidence: PMID:9473035 A 2,744-bp DNA fragment contained an open reading frame encoding cytosolic ALDH1, with 500 amino acids, which was located on chromosome XVI. PMID:9473035 The recombinant ALDH1 enzyme was found to be essentially NADP dependent |
| GO:0004030 aldehyde dehydrogenase [NAD(P)+] activity | IEA GO_REF:0000117 | TOO GENERAL | Summary: ARBA IEA aldehyde dehydrogenase [NAD(P)+] activity. Reason: Correct grouping-level term; redundant with experimental NADP+-specific terms. Supporting Evidence: file:yeast/ALD6/ALD6-uniprot.txt Reaction=an aldehyde + NADP(+) + H2O = a carboxylate + NADPH + 2 H(+); |
| GO:0004030 aldehyde dehydrogenase [NAD(P)+] activity | IMP PMID:9392076 The ALD6 gene of Saccharomyces cerevisiae encodes a cytosoli... | TOO GENERAL | Summary: IMP from Meaden et al. 1997: deletion of YPL061w (ALD6) eliminates the cytosolic Mg2+-activated acetaldehyde dehydrogenase activity. Reason: Loss of activity in the mutant plus N-terminal sequence identity of the purified enzyme establish ALD6 as the structural gene for the cytosolic ACDH. Correct. Supporting Evidence: PMID:9392076 Amino acids 2 to 16 of the protein encoded by YPL061w were found to be identical to the N-terminal 15 amino acids of the purified cytosolic, Mg(2+)-activated acetaldehyde dehydrogenase (ACDH) of S. cerevisiae. PMID:9392076 As expected, the cytosolic, Mg(2+)-activated ACDH activity had been lost from the mutants |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | ACCEPT | Summary: IEA cytoplasm from UniProt SubCell SL-0086. Reason: Correct; Ald6p is a cytosolic enzyme. Supporting Evidence: file:yeast/ALD6/ALD6-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm. |
| GO:0005739 mitochondrion | HDA PMID:14576278 The proteome of Saccharomyces cerevisiae mitochondria. | KEEP AS NON CORE | Summary: HDA mitochondrion from the Sickmann et al. 2003 mitochondrial proteome. Reason: Ald6p is one of the most abundant cytosolic proteins (about 135,000 molecules/cell) and lacks a mitochondrial presequence; its detection in purified mitochondria may reflect peripheral association or carry-over. Retain as a non-core location reported by a high-throughput study; its activity is cytosolic. Supporting Evidence: PMID:14576278 The proteins of highly pure yeast mitochondria were separated by several independent methods and analyzed by tandem MS. PMID:9473035 The N-terminal amino acids of ALDH1 were not indicative of a mitochondrial leader sequence. |
| GO:0005739 mitochondrion | HDA PMID:16823961 Toward the complete yeast mitochondrial proteome: multidimen... | KEEP AS NON CORE | Summary: HDA mitochondrion from Reinders et al. 2006. Reason: As above: high-throughput organellar proteome detection of an abundant cytosolic enzyme; non-core. 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... | KEEP AS NON CORE | Summary: HDA mitochondrion from Renvoise et al. 2014. Reason: As above: proteomic detection only; non-core. 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 | MARK AS OVER ANNOTATED | Summary: IBA is_active_in mitochondrion from PTN000916385, seeded by the yeast ALD4, ALD5 and ALD6 annotations. Reason: is_active_in asserts that the enzyme acts in mitochondria. That is true for the presequence-bearing Ald4p and Ald5p but not for Ald6p, which has no mitochondrial leader, fractionates entirely with the cytosol, and is the cytosolic Mg2+-activated ACDH of the PDH bypass. Target-specific evidence therefore argues against inheriting this assertion; the Ald6p entry among the donors reflects only its HDA proteome detections. Propagation Review Root cause: PROPAGATION BAD Failure modes: COMPARTMENT OR COMPLEX MISMATCH Sources checked: PANTHER:PTN000916385 · PTN000916385 SUPPORTS SOURCE BUT NOT TARGET Mitochondrial activity holds for presequence-bearing Ald4p/Ald5p; Ald6p lacks a leader and acts in the cytosol. Supporting Evidence: PMID:9473035 The N-terminal amino acids of ALDH1 were not indicative of a mitochondrial leader sequence. PMID:9473035 Cell fractionation confirmed that ALDH1 was found only in the cytosolic portion. |
| GO:0005739 mitochondrion | IDA PMID:16806052 MMI1 (YKL056c, TMA19), the yeast orthologue of the translati... | KEEP AS NON CORE | Summary: IDA mitochondrion from Rinnerthaler et al. 2006 (MMI1/TMA19 study). Reason: The cached abstract concerns Mmi1p translocation to the mitochondrial outer surface and does not mention Ald6p; the curator presumably saw Ald6p in mitochondrial fractions in the full text. Deferring to the curator for a located_in statement, but Ald6p activity is cytosolic, so this is non-core. Supporting Evidence: PMID:16806052 Mmi1p is stably but reversibly attached to the outer surface of the mitochondria and can be removed by digestion with proteinase K. |
| GO:0005829 cytosol | IDA PMID:16806052 MMI1 (YKL056c, TMA19), the yeast orthologue of the translati... | ACCEPT | Summary: IDA cytosol from Rinnerthaler et al. 2006. Reason: Consistent with all other evidence that Ald6p is cytosolic. Core location. Supporting Evidence: PMID:9473035 Cell fractionation confirmed that ALDH1 was found only in the cytosolic portion. |
| GO:0005829 cytosol | IMP PMID:9392076 The ALD6 gene of Saccharomyces cerevisiae encodes a cytosoli... | ACCEPT | Summary: IMP cytosol from Meaden et al. 1997: the cytosolic Mg2+-ACDH activity disappears in ald6 deletion mutants. Reason: Establishes that the cytosolic ACDH activity is Ald6p. Core location. Supporting Evidence: PMID:9392076 As expected, the cytosolic, Mg(2+)-activated ACDH activity had been lost from the mutants PMID:9392076 Amino acids 2 to 16 of the protein encoded by YPL061w were found to be identical to the N-terminal 15 amino acids of the purified cytosolic, Mg(2+)-activated acetaldehyde dehydrogenase (ACDH) of S. cerevisiae. |
| GO:0005829 cytosol | RCA GO_REF:0000123 | ACCEPT | Summary: RCA is_active_in cytosol from YeastPathways superpathway of glucose fermentation. Reason: Correct for Ald6p, the cytosolic enzyme of the PDH bypass. Supporting Evidence: PMID:9473035 Cell fractionation confirmed that ALDH1 was found only in the cytosolic portion. |
| GO:0006068 ethanol catabolic process | IEA GO_REF:0000041 | ACCEPT | Summary: IEA ethanol catabolic process from UniPathway UPA00780 (acetate from ethanol, step 2). Reason: Supported experimentally: ald6 deletion mutants cannot use ethanol as a carbon source, and Wang et al. show cytosolic ALDH1 (Ald6p) is involved in aerobic acetaldehyde oxidation. Supporting Evidence: PMID:9392076 Mutants deleted in YPL061w were also unable to use ethanol as a carbon source. PMID:9473035 The growth on glucose and ethanol indicated that the cytosolic ALDH1 is involved in oxidation of acetaldehyde produced during fermentation and is also involved in the aerobic oxidation of acetaldehyde. |
| GO:0006740 NADPH regeneration | IGI PMID:12584194 The ALD6 gene product is indispensable for providing NADPH i... | ACCEPT | Summary: IGI NADPH regeneration from Grabowska and Chelstowska 2003 (synthetic lethality with ZWF1). Reason: Ald6p reduces NADP+ while oxidizing acetaldehyde, and zwf1 ald6 double mutants are inviable; Ald6p directly performs an NADPH-generating reaction and is a major cytosolic NADPH source besides the oxidative pentose phosphate pathway. Core process. Supporting Evidence: PMID:12584194 A strain bearing a double ZWF1 ALD6 gene disruption is not viable. PMID:12584194 Thus, our results indicate the reaction catalyzed by Ald6p as an important source of reducing equivalents in the yeast cells. |
| GO:0009651 response to salt stress | IMP PMID:15146068 Identification of Ald6p as the target of a class of small-mo... | KEEP AS NON CORE | Summary: IMP response to salt stress from Butcher and Schreiber 2004: ald6 deletion confers resistance to high NaCl plus FK506. Reason: A genome-wide deletion-screen phenotype under calcineurin inhibition, linked to NADPH/NADP+ supply and glycerol production; Ald6p is not a dedicated salt-stress component. Retain as non-core, condition-specific involvement. Supporting Evidence: PMID:15146068 a genome-wide screen of approximately 4,700 haploid yeast deletion strains was undertaken for strains showing resistance to high NaCl plus FK506. PMID:15146068 This screen yielded a number of genes not previously implicated in salt stress, including ALD6, which encodes an NADP(+)-dependent aldehyde dehydrogenase |
| 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 | IMP PMID:11870853 Decreasing acetic acid accumulation by a glycerol overproduc... | ACCEPT | Summary: IMP acetate biosynthetic process from Eglinton et al. 2002: ald6 deletion decreased acetic acid production three-fold. Reason: Ald6p is the main source of acetate in the cytosolic PDH bypass during fermentation (confirmed by Remize et al. 2000 and Saint-Prix et al. 2004). Core process. Supporting Evidence: PMID:11870853 Deletion of the aldehyde dehydrogenase gene, ALD6, in wild-type and GPD2 overexpressing strains (GPD2-OP) decreased acetic acid production by three- and four-fold, respectively. PMID:9392076 This enzyme is thought to be involved in the production of acetate from which cytosolic acetyl-CoA is then synthesized. |
| GO:0019658 bifid shunt | RCA GO_REF:0000123 | REMOVE | Summary: RCA bifid shunt from YeastPathways superpathway of glucose fermentation. Reason: The bifid shunt is a bifidobacterial phosphoketolase pathway absent from S. cerevisiae; mapping artefact. Ald6p's fermentative role is captured by acetate biosynthetic process. |
| 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: Ald6p (ALDH1) is essentially NADP-dependent; correct. Supporting Evidence: PMID:9473035 The recombinant ALDH1 enzyme was found to be essentially NADP dependent file:yeast/ALD6/ALD6-uniprot.txt Reaction=an aldehyde + NADP(+) + H2O = a carboxylate + NADPH + 2 H(+); |
| GO:0033721 aldehyde dehydrogenase (NADP+) activity | IEA GO_REF:0000120 | ACCEPT | Summary: IEA from EC 1.2.1.4 / Rhea mapping. Reason: Correct; matches experimental NADP+-dependent activity. Supporting Evidence: file:yeast/ALD6/ALD6-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 (aldehyde + NADP+ -> carboxylate, EC 1.2.1.4). Reason: This is the reaction Ald6p performs in the cytosolic PDH bypass; correct. Supporting Evidence: file:yeast/ALD6/ALD6-uniprot.txt Reaction=an aldehyde + NADP(+) + H2O = a carboxylate + NADPH + 2 H(+); |
| GO:0046394 carboxylic acid biosynthetic process | IEA GO_REF:0000117 | TOO GENERAL | Summary: ARBA IEA carboxylic acid biosynthetic process. Reason: Very general ancestor of acetate biosynthetic process, which is already annotated with experimental support. |
| 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 records acetaldehyde + NADP+ -> acetate for Ald6p with Km 24 uM for acetaldehyde and Vmax 24 umol/min/mg. This is the core MF. Supporting Evidence: file:yeast/ALD6/ALD6-uniprot.txt Reaction=acetaldehyde + NADP(+) + H2O = acetate + NADPH + 2 H(+); PMID:9473035 The recombinant ALDH1 enzyme was found to be essentially NADP dependent |
| GO:0140088 acetaldehyde dehydrogenase (NADP+) activity | IEA GO_REF:0000116 | ACCEPT | Summary: IEA from Rhea mapping (RHEA:25298). Reason: Correct; matches experimental activity. Supporting Evidence: file:yeast/ALD6/ALD6-uniprot.txt Reaction=acetaldehyde + NADP(+) + H2O = acetate + NADPH + 2 H(+); |
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Download this section (compressed HTML)Q: Is the mitochondrial detection of Ald6p in proteomic and fractionation studies a genuine peripheral association with the outer membrane, or contamination by an abundant cytosolic protein?
Q: How is flux partitioned between Ald6p-derived NADPH and the oxidative pentose phosphate pathway under different carbon sources?
Experiment: Use protease-protection and fluorescence microscopy of endogenously tagged Ald6p in wild-type cells to test for any mitochondria-associated pool.
Cytosolic aldehyde dehydrogenase; activated by Mg2+ and utilizes NADP+ as the preferred coenzyme; required for conversion of acetaldehyde to acetate; constitutively expressed; localizes to the mitochondrial outer surface upon oxidative stress; negative regulator of nonselective autophagy; Stb5p directly regulates the expression of ALD6 mRNA and directly binds to the ALD6 promoter
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