Stoffwechselprodukte von Mikroorganismen, 117.L-Arginyl-D-allo-threonyl-L-phenylalanin, ein Aminosäure-Antagonist aus dem PilzKeratinophytonterreum

Rhizocticin A, an antifungal phosphono-oligopeptide of Bacillus subtilis ATCC 6633: biological properties

Rhizocticin A, the main component of the antifungal, hydrophilic phosphono-oligopeptides of Bacillus subtilis ATCC 6633, was used for sensitivity testing and experiments into the molecular mechanism of the antibiotic action. Budding and filamentous fungi as well as the cultivated nematode Caenorhabditis elegans were found to be sensitive, whereas bacteria and the protozoon Paramecium caudatum were insensitive. Rhizoctonia solani was inhibited in agar dilution tests but not in diffusion tests. The antifungal effect of rhizocticin A was neutralized by a variety of amino acids and oligopeptides. Oligopeptide influence was mainly understood as transport antagonism, and it was concluded that the antibiotic enters the recipient cell via the peptide transport system. L- and D-cystine were also identified as potent, general antagonists of the oligopeptide transport. The rhizocticin-antagonism of four other amino acids was taken as a clue to the site of action. Provided that rhizocticin A is split by peptidases of the target cell into inactive L-arginine and toxic L-2-amino-5-phosphono-3-cis-pentenoic acid (L-APPA), the latter may interfere with the threonine or threonine-related metabolism.

[Antibiotically active tripeptides of the sequence L-arg-D-X-L-phe] (author's transl)]

Five tripeptides with the sequence L-Arg-D-X-L-Phe showed antibiotic activity on fungi and on some pathogenic moulds. The action of the peptides could be neutralized in the cross-strip test by the L-amino acid corresponding to the D-amino acid in the middle position.