Fostriecin is an antibiotic originally derived from Streptomyces pulveraceus. This compound has been shown to inhibit the catalytic activity of partially purified Topo II (type II topoisomerase) in a non-competitive manner. Unlike other known inhibitors of this enzyme, fosteriecin has not been observed to cause DNA strand breaks in L1210 cells, suggesting that it does not stabilize a cleavable complex. Furthermore, in the same experiment, this agent was demonstrated to cause a block in the G2 phase of the cell cycle. Fostriecin has also displayed a strong capacity to inhibit protein phosphatase 1 (PP1) and protein phosphatase 2A (PP2A).
