Über den Stoffwechsel von Oligopeptiden und Diketopiperazinen in Claviceps-Arten: On the Metabolism of Oligopeptides and Diketopiperazines in Claviceps Species

Abstract

Using a strain of Claviceps purpurea (Pepty 695) which produces ergocornine and ergokryptine feeding experiments were performed to clarify the formation of the peptide portion of ergot alkaloids. The following labelled dipeptides and for the first time a tripeptide were administered to submerged cultures during the idiophase: [L-prolyl-U-14C]-L-alanine; [L-prolyl-U-14C]-glycin; L-valyl-[L-leucinU- 14C] and L-valyl-L-leucyl-[L-prolin-U-14C]. After degradation the distribution of radioactivity in each ergotoxine alkaloid was determined. The labeling of the protein fraction and of the particular amino acid in the pool of mycelial amino acids were also measured. Similar experiments were performed with [L-leucyl-U-14C]-prolyl-lactam and L-leucyl-[L-prolyl-U-14C]-lactam. It was found that the peptides are split by the fungus into the corresponding amino acids prior to incorporation. Aps parently the alkaloid spectrum is not influenced by feeding peptides to intact mycelium of Claviceppurpurea. The occurrence of diketopiperazines in sclerotia and saprophytic cultures of various high yielding ergot-strains was investigated. Only scattered in young submerged mycelium of strain Pepty 695 leu-pro-Iactam and val-pro-lactam was found. There was no correlation between diketopiperazine content and alkaloid formation in our material. Washed mycelium of different C. purpurea strains is able to split Leu-Pro-lactam. The clavine strain SD 58 and a strain of C. paspali do not attack this diketopiperazine. Our results seem to indicate this might be due to the lack of a specific diketopiperazine transport system, because there was no uptake of Leu-Pro-lactam by these particular strains derived from grass-ergot.