Urea treatment and pronase digestion of antitumor protein antibiotics, auromomycin and neocarzinostatin.

Low molecular weight substances were separated from antitumor protein antibiotics, auromomycin and neocarzinostatin, by Sephadex G50 column chromatography, after denaturation with 8 M urea. The low molecular weight fraction of auromomycin, but not the protein fraction, showed antimicrobial and DNA-cleaving activities. More than 90% of the auromomycin and neocarzinostatin proteins were digested with a high concentration of pronase E. The digested samples of both antibiotics exhibited the same degree of activities as the original drugs in the inhibition of growth and DNA synthesis of mouse lymphoblastoma L5178Y cells and in causing strand scission of isolated PM2 phage DNA. The low molecular weight chromophores were recovered on Sephadex G50 column from the pronase-digested antibiotics. The results suggest that the in vitro biological activity of auromomycin and neocarzinostatin are principally attributed to the non-protein compounds of low molecular weight.