TOPOSTIN, A NOVEL INHIBITOR OF MAMMALIAN DNA TOPOISOMERASE I FROM FLEXIBACTER TOPOSTINUS SP. NOV.

II. PURIFICATION AND SOME PROPERTIES OF TOPOSTIN

Abstract

We describe the isolation of inhibitors of mammalian DNA topoisomerase I, named topostins, from a culture broth of Flexibacter topostinus sp. nov. and some properties of the inhibitors. Topostins Al, A2 and B were isolated by differential solubility in solvents, adsorption chromatography on silica gel and gel nitration on a Sephadex LH-20 column. Topostins Al, A2 and B had specific activities of 4, 700, 16, 000 and 22, 000 U/mg, respectively. The most active metabolite topostin B comprised two components with MW of 567 and 553 in an equimolar ratio.