Studies in the biochemistry of micro-organisms. 108. Metabolites of Alternaria tenuis Auct.: the biosynthesis of tenuazonic acid

Abstract

A strain of Alternaria tenuis. growing on Czapek-Dox medium, has been shown to incorporate over 4% of the 14C from added sodium [1.14C] acetate into tenuazonic acid. Over 94% of the radioactivity is shared equally between the lactam and side-chain carbonyl groups; the remainder is shared equally between C-4 of the ring and the [omega]-carbon atom of the sec.-butyl side chain. It is suggested that tenuazonic acid is synthesized from two molecules of acetate and a molecule of L-isoleucine. The relationship of this pathway to the biosynthesis of fungal tetronic acids is discussed. During growth of A. tenuis in undisturbed surface culture, the concentration of tenuazonic acid increases rapidly during the second week, then decreases to a minimum and rises again.