Mycotoxins - Their Biosynthesis in Fungi: Ochratoxins - Metabolites of Combined Pathways.

Little work has been done on the biosynthesis of ochratoxins. Nevertheless. a scheme based on known chemical and enzymatic reactions and incorporating known facts about ochratoxin biosynthesis is proposed as a working model. The scheme calls for formation of an unbranched pentaketide from acetyl and malonyl CoA, its cyclization and aromatization to an is ocoumarin, methylation and oxidation to the carboxy derivative which is chlorinated by chloroperoxidase before acyl activation for reaction with an ester of phenylalanine which arises via the shikimic acid pathway. The amide, ochratoxin A, is considered the final product of this biosynthetic pathway.