We have recently described a mitochondrial fatty acid beta-oxidation pathway in Aspergillus nidulans (Maggio-Hall & Keller. 2004. Mol. Microbiol. 54: 1173-85). Here we describe the disruption and characterization of another gene in the pathway, that encoding the acyl-CoA dehydrogenase (scdA). The phenotypes of the scdA deletion strain further confirmed this pathway's role in degrading short-chain fatty acids (C4-C6) as well as the amino acids isoleucine and valine. Unlike the previously described disruption of the enoyl-CoA hydratase enzyme in the pathway, the scdA mutant showed no defect during growth on long- and very long-chain fatty acids. Furthermore, the scdA echA double mutant also grew just as well as wild type on these fatty acids, indicating that the echA deletion phenotype—extremely restricted growth on long- and very long-chain fatty acids—was due entirely to toxicity of accumulated intermediates and not a failure to metabolize the fatty acids. Biochemical analysis of the scdA (dehydrogenase) mutant 12 h after transfer to hexanoate-containing medium showed that whole-cell enoyl-CoA hydratase activity was significantly diminished, suggesting a build-up of short-chain fatty acids inhibits other beta-oxidation pathways in the cell. This inhibition is not at the level of transcription, based on Northern analysis of identified enoyl-CoA hydratase-encoding genes (echA and foxA).
Full conference title:
23rd Fungal Genetics Conference
- Fungal Genetics Conference 23rd (2002)