Generation of Free Radicals from Neocarzinostatin Mediated by NADPH/Cytochrome P-450 Reductase via Activation of Enediyne Chromophore

Keizo Sato, Takaaki Akaike, Moritaka Suga, Masayuki Ando, Hiroshi Maeda

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)

Abstract

Neocarzinostatin (NCS) is one of the most potent antitumor agents. It contains a chromophore of a unique enediyne structure as its prosthetic group. Here, we report the generation of free radicals from NCS by the NADPH/cytochrome (cyt) P-450 reductase system. Free radical species, which were generated in the reaction mixture of NCS/NADPH/cyt P-450 reductase, were identified by using electron spin resonance spin trapping with 5,5-dimethyl-1-pyrroline N-oxide (DMPO). The spin adducts of superoxide and hydroxyl radical (DMPO-OOH and DMPO-OH, respectively) were generated in the reaction of NCS with the NADPH/cyt P-450 reductase system. From kinetic analyses of DMPO-OOH generation as a function of the concentration of NCS, the Vmax/Km value of the reaction was 0.4 × 106 M-1min-1. In addition, we identified thiyl radical generation in this system in the presence of glutathione. These results indicate that NCS is a potent generator of free radicals in cells where cyt P-450 reductase is available. Moreover, it seems that free radicals, generated by enzymatic activation of NCS, are involved in cytotoxicity of NCS as well as in DNA damage.

Original languageEnglish
Pages (from-to)1716-1723
Number of pages8
JournalBiochemical and biophysical research communications
Volume205
Issue number3
DOIs
Publication statusPublished - 1994 Jan 1
Externally publishedYes

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology

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