Abstract
A pathogenic fungus of apple trees. Alternaria alternata (AKI-3 strain) produced two cyclic peptides alternariolide 1 (AM-Toxin I) and tentoxin 2. 1 is known as a host-specific toxin which caused brown necrotic spots on trees of susceptible cultivar. 2 is also known a potent phytotoxin against several plant including apple trees. Now the fungi were grown with ^<14>C-labelled amino acids (U-L-Ser, U-L-Ala, U-L-Phe, U-Gly) in Richard's medium for 2 weeks at 28℃. Both the peptides 1 and 2 were isolated and purified by silica gel TLC. Incorporation of each amino acid into 1 (6.5×10^<-5>〜1.9×10^<-3>μCi/μmole) and 2 (7.9×10^<-5>〜2.8×10^<-3>μCi/μmole) was confirmed. From the radioactivities of components separated by paper chromatography of the hydrolysis of 1, metabolic precursors of dehydroalanine and an aromatic amino acid moieties in 1 may be considered to be serine and phenylalanine, respectively.
