The inhibition of clavine biosynthesis by 5-fluorotryptophan; a useful tool for the study of regulatory and biosynthetic relationships in Claviceps

Abstract

Clavine alkaloid production in submerged cultures of various Claviceps strains was inhibited by 0.25 m M 5-fluorotryptophan (5-Ftrp). The inhibition was removed by washing the cultures, or by addition of 50 m M tryptophan. Lower doses of tryptophan (0.25-25.0 raM) were ineffective. Addition of cycloheximide a n d / o r 8-hydroxyquinoline (8-HOQ) to the inhibited cultures 24 and 48 h prior washing increased the rate of alkaloid synthesis in washed cultures (superinduction) and the rate of clavine synthesis was proportional to the length of 8-HOQ pretreatmento The addition of 0.25 m M tryptophan in washed cultures also stimulated alkaloid synthesis, but only for 2-3 days, then production in the cultures without tryptophan was higher. Cultures of Claviceps strains 59 and EK-10 inhibited with 5-Ftrp were capable of converting chanoclavine into further clavine pathway products. 5-Fluorotryptophan probably acts as an inhibitor of the first enzyme of the clavine pathway. However, the superinduction suggests the presence of a labile regulatory protein controlling clavine biosynthesis.