ABSTRACTOchratoxin A (OTA), a mycotoxin produced byAspergillusandPenicilliumspecies, is composed of a dihydroisocoumarin ring linked to phenylalanine, and its biosynthetic pathway has not yet been completely elucidated. Most of the knowledge regarding the genetic and enzymatic aspects of OTA biosynthesis has been elucidated inPenicilliumspecies. InAspergillusspecies, onlypksgenes involved in the initial steps of the pathway have been partially characterized. In our study, the inactivation of a gene encoding a nonribosomal peptide synthetase (NRPS) in OTA-producingA. carbonariusITEM 5010 has eliminated the ability of this fungus to produce OTA. This is the first report on the involvement of annrpsgene product in OTA biosynthetic pathway in anAspergillusspecies. The absence of OTA and ochratoxin α, the isocoumaric derivative of OTA, and the concomitant increase of ochratoxin β, the dechloro analog of ochratoxin α, were observed in the liquid culture of transformed strain. The data provide the first evidence that the enzymatic step adding phenylalanine to polyketide dihydroisocoumarin precedes the chlorination step to form OTA inA. carbonariusand that ochratoxin α is a product of hydrolysis of OTA, giving an interesting new insight into the biosynthetic pathway of the toxin.
New Insight into the Ochratoxin A Biosynthetic Pathway through Deletion of a Nonribosomal Peptide Synthetase Gene in Aspergillus carbonarius
