Biochemical studies on bactobolin in relation to actinobolin.

Bactobolin, a new congener of actinobolin, was isolated from the culture broths of a Pseudomonas sp.'. In spite of close structural similarity1,2) the two antibiotics differ considerably in their biological activity, especially in antitumor activity, bactobolin being stronger than actinobolin" s, 4) . The latter antibiotic has been shown to primarily inhibit protein synthesis in bacterial cellsb' and, more precisely, to interfere with binding of aminoacyl tRNA to the ribosome in tumor cells8' . The present study was initiated to reveal the biochemical basis for the difference in the biological activity of the two antibiotics. A recent finding that bactobolin was not as effective on T-cell derived leukemic cells as on B-cell derived cells7) is also dealt with as an extension of this study. The biological and biochemical activity of actinobolin and bactobolin was determined in various assay systems with the results summarized in Table 1. With respect to inhibition of growth