Mitochondrial beta-oxidation in Aspergillus nidulans.

Area of Science:

• Biochemistry
• Molecular Biology
• Mycology

Background:

• Beta-oxidation (beta-ox) is a metabolic process for breaking down fatty acids.
• In yeasts like Saccharomyces cerevisiae, beta-ox occurs solely in peroxisomes.
• This has led to the assumption that fungi lack mitochondrial beta-ox.

Purpose of the Study:

• To investigate the presence and function of beta-oxidation pathways in the filamentous fungus Aspergillus nidulans.
• To determine the subcellular localization of key beta-oxidation enzymes.

Main Methods:

• Generation and analysis of gene disruption mutants (DeltafoxA and DeltaechA).
• Assessment of fungal growth on fatty acids of varying chain lengths (short, long, very long).
• Enzyme activity assays and subcellular localization studies using fluorescent protein fusions.

Main Results:

• Aspergillus nidulans exhibits both peroxisomal and mitochondrial beta-oxidation.
• Disruption of the peroxisomal pathway (DeltafoxA) impaired growth on very long-chain fatty acids.
• Disruption of the enoyl-CoA hydratase gene (echA) severely affected growth on all chain lengths and impacted isoleucine/valine metabolism.

Conclusions:

• The filamentous fungus Aspergillus nidulans utilizes both peroxisomal and mitochondrial beta-oxidation.
• The enoyl-CoA hydratase (EchA) enzyme plays a critical role in both pathways and is essential for utilizing various fatty acids and amino acids.