D-arabinono-1,4-lactone oxidase that catalyzes the terminal step in fungal D-erythroascorbic acid biosynthesis. This mitochondrial outer membrane-anchored flavoprotein oxidizes D-arabinono-1,4-lactone using molecular oxygen as electron acceptor, producing D-erythroascorbic acid (a 5-carbon analog of vitamin C) and hydrogen peroxide. The enzyme contains a covalently bound FAD cofactor and plays a critical role in cellular antioxidant defense, with deletion mutants showing hypersensitivity to oxidative stress. Recent studies in S. cerevisiae reveal a potential moonlighting function where Alo1 binds the myosin V motor Myo2 and aids in mitochondrial inheritance, particularly under oxidative stress conditions (PMID:39775849), though this role remains to be confirmed in S. pombe.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005739 mitochondrion | IBA GO_REF:0000033 | ACCEPT | Summary: Annotation correctly identifies mitochondrial localization based on ortholog evidence. While more specific localization to outer membrane might be possible, the mitochondrial localization is confirmed. Supporting Evidence: file:SCHPO/alo1/alo1-deep-research-falcon.md ALO was purified from the **mitochondrial fraction** |
| GO:0003885 D-arabinono-1,4-lactone oxidase activity | IBA GO_REF:0000033 | ACCEPT | Summary: Correct molecular function annotation based on phylogenetic inference from S. cerevisiae ortholog. Supporting Evidence: file:SCHPO/alo1/alo1-deep-research.md S. cerevisiae ALO1 was biochemically confirmed to catalyze EASC production. The enzyme produces D-erythroascorbic acid, a five-carbon analog of vitamin C found in fungi file:SCHPO/alo1/alo1-deep-research-falcon.md ALO catalyzes the **terminal oxidation step** in **D-erythroascorbic acid (EASC)** biosynthesis: **D-arabinono-1,4-lactone β D-erythroascorbic acid** file:SCHPO/alo1/alo1-deep-research-falcon.md Purified budding-yeast ALO oxidized **D-arabinono-1,4-lactone**, **L-gulono-1,4-lactone**, and **L-galactono-1,4-lactone** |
| GO:0003885 D-arabinono-1,4-lactone oxidase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Redundant with IBA annotation above. The molecular function is correct. |
| GO:0016020 membrane | IEA GO_REF:0000002 | MODIFY | Summary: Too general. Protein specifically localizes to mitochondrial outer membrane based on evidence from orthologs. Proposed replacements: mitochondrial outer membrane |
| GO:0016491 oxidoreductase activity | IEA GO_REF:0000043 | REMOVE | Summary: Too general. The specific activity GO:0003885 (D-arabinono-1,4-lactone oxidase activity) is already annotated. |
| GO:0016899 oxidoreductase activity, acting on the CH-OH group of donors, oxygen as acceptor | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: Correct but could be more specific. This parent term encompasses the specific activity GO:0003885. |
| GO:0031966 mitochondrial membrane | IEA GO_REF:0000044 | MODIFY | Summary: Correct but not specific enough. Evidence indicates outer membrane localization. Falcon ortholog evidence independently supports a mitochondrial membrane association (S. cerevisiae ALO purified from the mitochondrial fraction and predicted to be an integral membrane protein), though falcon does not resolve inner vs outer membrane; the outer-membrane specificity rests on the Myo2-interaction study. Proposed replacements: mitochondrial outer membrane Supporting Evidence: file:SCHPO/alo1/alo1-deep-research-falcon.md sequence analysis predicted an **integral membrane protein** with a **transmembrane segment (aa 172β188)**, supporting a **mitochondrial membrane** localization in budding yeast |
| GO:0050660 flavin adenine dinucleotide binding | IEA GO_REF:0000002 | ACCEPT | Summary: Correct annotation. The enzyme contains a conserved FAD-binding domain essential for oxidase activity. Supporting Evidence: file:SCHPO/alo1/alo1-deep-research.md S. cerevisiae ALO1 has a conserved histidine that binds FAD, and sequence analysis revealed a covalent FAD-binding site in the enzyme file:SCHPO/alo1/alo1-deep-research-falcon.md ALO is a **flavoenzyme** with **covalently bound FAD** file:SCHPO/alo1/alo1-deep-research-falcon.md fungal/animal oxidase-type enzymes (ALO/GULO) commonly feature a **covalent histidyl-FAD** and use **O2** as electron acceptor |
| GO:0071949 FAD binding | IEA GO_REF:0000002 | REMOVE | Summary: Redundant with GO:0050660. Both refer to FAD binding. |
| GO:0070485 dehydro-D-arabinono-1,4-lactone biosynthetic process | ISO GO_REF:0000024 | ACCEPT | Summary: Correct biological process annotation. The enzyme produces dehydro-D-arabinono-1,4-lactone (D-erythroascorbic acid) as confirmed in S. cerevisiae. Supporting Evidence: file:SCHPO/alo1/alo1-deep-research.md In S. cerevisiae, ALO1 is essential for endogenous erythroascorbate production β alo1Ξ mutants completely lack D-erythroascorbic acid and ALO activity file:SCHPO/alo1/alo1-deep-research-falcon.md the **mitochondrial D-arabinono-1,4-lactone oxidase uses oxygen as an electron acceptor**, producing D-erythroascorbate and hydrogen peroxide file:SCHPO/alo1/alo1-deep-research-falcon.md alo1 deletion** abolished detectable **EASC** and ALO activity; multicopy **ALO1** increased intracellular **EASC ~6.9-fold** and ALO activity **~7.3-fold** |
| GO:0005739 mitochondrion | HDA PMID:16823372 ORFeome cloning and global analysis of protein localization ... | ACCEPT | Summary: Experimentally confirmed mitochondrial localization. Could be more specific (outer membrane) but experimental evidence confirms mitochondrial association. Supporting Evidence: PMID:16823372 ORFeome cloning and global analysis of protein localization in the fission yeast Schizosaccharomyces pombe. |
| GO:0005741 mitochondrial outer membrane | ISO GO_REF:0000024 | ACCEPT | Summary: Correct and specific localization based on ortholog evidence from S. cerevisiae. Supporting Evidence: file:SCHPO/alo1/alo1-deep-research-alt.md Alo1 was found anchored in the mitochondrial outer membrane and capable of recruiting Myo2 to mitochondria |
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Download this section (compressed HTML)Q: Does S. pombe alo1 have a moonlighting function in mitochondrial inheritance similar to S. cerevisiae ALO1?
Q: What is the substrate specificity of S. pombe Alo1 and can it produce L-ascorbate from L-gulonolactone?
Q: Is alo1 expression regulated by oxygen availability or oxidative stress response pathways in S. pombe?
Q: How does loss of alo1 affect cellular redox balance and what compensatory mechanisms are activated?
Experiment: Create and characterize alo1Ξ knockout strain to test oxidative stress sensitivity and D-erythroascorbate dependence
Experiment: Biochemically characterize purified Alo1 enzyme for substrate specificity, kinetics, and FAD cofactor binding
Experiment: Track mitochondrial inheritance in alo1Ξ cells during cell division using live-cell imaging with fluorescent markers
Experiment: Identify Alo1 protein interaction partners by co-immunoprecipitation and mass spectrometry, especially testing for Myo52 binding
Experiment: Test if alo1 expression is regulated by oxygen levels or oxidative stress using promoter-reporter assays and RNA-seq
Experiment: Determine if Alo1 can produce L-ascorbate from L-gulonolactone using in vitro enzymatic assays and LC-MS product analysis
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Download this section (compressed HTML)π View Pathway Visualization Interactive pathway diagram with detailed annotations