INCORPORATION OF ¹⁴C-LABELED COMPOUNDS INTO SINEFUNGIN (A9145), A NUCLEOSIDE ANTIFUNGAL ANTIBIOTIC

Abstract

CStreptomyces griseolus produces a complex of antifungal nucleoside antibiotics that contain an ornithine residue linked to the ribose moiety of adenosine. ¹⁴C-Labeled compounds were added to cultures of S. griseolus (≈0.5μCi/ml culture broth) and the amount of label incorporated into the two major antifungal components (sinefungin and factor C) was measured. Substantial incorporation (16-52%) was obtained with adenosine [8-¹⁴C], ATP [¹⁴C(u)], adenine [8-¹⁴C], L-ornithine [¹⁴C (u)], and DL-citrulline [5-¹⁴C]. Glycine, glucose, L-arginine, and acetate were incorporated to the extent of 1.7-4.7%. Studies were conducted on the fermentation time course and on the time dependence of label incorporation in order to optimize the incorporation of labeled adenine into sinefungin. Adenine [8-¹⁴C] incorporation and sinefungin specific activity were highest 48 hours after label addition and both declined during subsequent incubation. As much as 43% of the labeled adenine was incorporated into the antibiotic and sinefungin was produced with a specific activity of 24.8μCi/mg. The labeling experiments suggest that a preformed adenine derivative (e.g., an adenine nucleotide) and ornithine (or a closely related metabolite) are direct biosynthetic precursors of sinefungin.