Biological properties and mode of action of clavams

The clavams valclavam and hydroxyethylclavam were both bacteriostatic and fungistatic. The molecular basis for growth inhibition of Escherichia coli was a non-competitive inhibition of homoserine-O-succinyltransferase (EC 2.3.1.46), thus blocking methionine biosynthesis. Eucaryotes such as Saccharomyces cerevisiae were inhibited by a different mode of action. Instead of interfering with methionine biosynthesis, the clavams inhibited the formation of RNA in living cells, although the RNA-polymerases of isolated yeast nuclei were not inhibited. The action of valclavam on E. coli was dependent on functional peptide transport systems.Abbreviations CoA coenzyme A - mic mimimal inhibitory concentration - SAM S-adenosylmethionine - TCA trichloroacetic acid Offprint requests to: H. ZähnerMetabolic products of microorganisms 241 (Metabolic products of microorganisms, 240. Rohr J, Zeeck A (1987) Urdamycins, new angucycline antibiotic form Streptomyces fradiae. II. Structural studies of urdamycin B to F. J Antibiotics, in press