Ustethylin Biosynthesis Implies Phenethyl Derivative Formation in Aspergillus ustus

Area of Science:

• Natural Product Chemistry
• Molecular Biology
• Mycology

Background:

• Aspergillus ustus is a fungal species known to produce various secondary metabolites.
• Phenethyl derivatives represent a class of compounds with diverse biological activities.
• The biosynthetic pathways of many fungal secondary metabolites remain unelucidated.

Purpose of the Study:

• To isolate and characterize a novel phenethyl derivative from Aspergillus ustus.
• To elucidate the biosynthetic pathway of the isolated compound, ustethylin A.
• To identify the enzymes involved in the assembly and modification of the ustethylin A core structure.

Main Methods:

• Isolation and purification of ustethylin A using chromatographic techniques.
• Gene deletion studies in Aspergillus ustus to identify key biosynthetic genes.
• Isotope labeling experiments to trace the origin of the carbon backbone.
• Heterologous expression of candidate genes in a heterologous host.

Main Results:

• Ustethylin A, a highly oxygenated phenethyl derivative, was isolated from Aspergillus ustus.
• The phenethyl core structure is assembled from malonyl-CoA via a polyketide synthase with a methyltransferase domain.
• Propionate is converted to malonyl-CoA and incorporated into the molecule.
• Three oxidoreductases and one O-methyltransferase are responsible for modifying the core structure to yield ustethylin A.

Conclusions:

• The biosynthetic pathway of ustethylin A involves a unique polyketide synthase and subsequent enzymatic modifications.
• This study provides insights into the assembly of phenethyl derivatives in fungi.
• The identified enzymes offer potential targets for engineering novel compounds.