Mycotoxins - Their Biosynthesis in Fungi: Patulin and Related Carcinogenic Lactones

A brief introduction to the mycotoxin, patulin is followed by a summary of the early contributions which demonstrated that patulin and its precursor, 6-methylsalicylic acid were derived from acetyl-CoA and hence are polyketides. The polyketide lactones, triacetic acid lactone, mycophenolic acid, patulin, penicillic acid and multicolic acid are compared with respect to their biosynthetic origins and the obscured sequence of acetate units in the latter three lactones is discussed. The current status of the patulin biosynthetic pathway is described with special emphasis on recent findings which have altered the late or post-gentisaldehyde portion of the pathway. This new appreciation of the patulin pathway is then extrapolated to the closely related γ-lactones, penicillic acid and multicolic acid. Pathways analogous to that of patulin are proposed for these two lactones and are discussed. These biosynthetic relationships are then related to the co-occurrence of some of these lactones in cultures of the same fungus.