cyclo-(L-Phenylalanyl-L-seryl) as an intermediate in the biosynthesis of gliotoxin

Abstract

Feeding experiments with the four stereoisomers of cyclo-(phenylalanylseryl) have shown that only the LL-isomer is incorporated efficiently (48%) into gliotoxin in ‘Trichoderma viride’(Gliocladium deliquescens). cyclo-(L-[4′-³H]Phenylalanyl-L-[3-¹⁴C]seryl) gave gliotoxin with essentially unchanged ³H : ¹⁴C ratio. Successive feedings of non-radioactive cyclo-(L-phenylalanyl-L-seryl) and L-[U-¹⁴C]phenylalanine to cultures of T. viride led to the recovery of cyclo-(L-phenylalanyl-L-seryl) containing 1.3% of the radioactivity of the amino-acid. It is concluded that the cyclo-dipeptide is a natural metabolite of T. viride and is either an intermediate, or is interconvertible with an intermediate, on the biosynthetic pathway from phenylalanine to gliotoxin.