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© 1998 Federation of European Biochemical Societies.

Syringomycin E, syringopeptin 22-A and syringopeptin 25-A, the main phytotoxins isolated from cultures of several strains ofPseudomonas syringaepv.syringae, were separately tested for their activity on some mitochondrial functions. It was shown that syringopeptins were several-fold more active uncouplers of oxidative phosphorylation than syringomycin E. They were also more active in increasing the respiration of succinate and NADH and the hydrolysis of ATP in isolated maize and pea mitochondria, and in decreasing the membrane potential of those mitochondria. These results explain the apparent contrast between the findings obtained some years ago with toxin preparations which had been considered homogeneous, but in fact contained multiple forms of syringomycins and syringopeptins, and those obtained using pure syringomycin E.

The covalent structure and most of the stereochemistry of the pseudomycins, bioactive metabolites of a transposon-generated mutant of a Pseudomonas syringaewild-type strain proposed for the biological control of Dutch elm disease, have been determined. While two pseudomycins are identical to the known syringopeptins 25-A and 25-B, pseudomycins A, B, C, C′ are new lipodepsinonapeptides. For all of these the peptide moiety corresponds to l-Ser- d-Dab- l-Asp- l-Lys- l-Dab- l-aThr-Z-Dhb- l-Asp(3-OH) - l-Thr(4-Cl) with the terminal carboxyl group closing a macrocyclic ring on the OH group of the N-terminal Ser. This is in turn N-acylated by 3,4-dihydroxytetradecanoate in pseudomycin A, by 3-hydroxytetradecanoate in pseudomycin B, by 3,4-dihydroxyhexadecanoate in pseudomycin C, and by 3-hydroxyhexadecanoate in pseudomycin C′. Some preliminary data on the biological activity of pseudomycin A are reported.

The structure of the fuscopeptins, bioactive lipodepsipeptides produced in culture by the gramineae pathogen Pseudomonas fuscovaginae, has been determined. The combined use of FAB mass spectrometry, NMR spectroscopy and chemical and enzymatic procedures allowed one to define a peptide moiety corresponding to ZDhb‐DPro‐LLeu‐DAla‐DAla‐DAla‐DAlaDVal‐Gly‐DAla‐DVal‐DAla‐DVal‐ZDhb‐DaThr‐LAla‐LDabDDab‐LPhe with the terminal carboxyl group closing a macrocyclic ring on the hydroxyl group of the allothreonine residue. The N‐terminus is in turn acylated by 3‐hydroxyoctanoate in fuscopeptin A and 3‐hydroxydecanoate in fuscopeptin B. Some preliminary data on the biological activity of fuscopeptins are also reported.

The covalent structure and most of the stereochemistry of the pseudomycins, bioactive metabolites of a transposon‐generated mutant of a Pseudomonas syringaewild‐type strain proposed for the biological control of Dutch elm disease, have been determined. While two pseudomycins are identical to the known syringopeptins 25‐A and 25‐B, pseudomycins A, B, C, C′ are new lipodepsinonapeptides. For all of these the peptide moiety corresponds to l‐Ser‐d‐Dab‐l‐Asp‐l‐Lys‐l‐Dab‐l‐aThr‐Z‐Dhb‐l‐Asp(3‐OH) ‐l‐Thr(4‐Cl) with the terminal carboxyl group closing a macrocyclic ring on the OH group of the N‐terminal Ser. This is in turn N‐acylated by 3,4‐dihydroxytetradecanoate in pseudomycin A, by 3‐hydroxytetradecanoate in pseudomycin B, by 3,4‐dihydroxyhexadecanoate in pseudomycin C, and by 3‐hydroxyhexadecanoate in pseudomycin C′. Some preliminary data on the biological activity of pseudomycin A are reported.

A new syringopeptin was purified from a culture ofPseudomonas syringaepv.syringaeNCPPB 3869 isolated from laurel and its structure deduced by mass spectrometry and Edman degradation. It differs from syringopeptin 25A only for the C-terminal amino acid residue, which is Phe instead of Tyr. The phytotoxicity and some other biological activities of the new metabolite are comparable to those of syringopeptin 25A.