title: Protoporphyrin IX catalyzed hydrogen peroxide to generate singlet oxygen.
abstract: OBJECTIVE
  To study the role of protoporphyrin IX (pPIX) in mitochondrial metabolism of hydrogen peroxide (H2O2).
  
  
  METHODS
  O2 (-) specific fluorescent markers DMA (9,10-dimerthylanthracence) and SOSG (Singlet Oxygen Sensor Green reagent) were used for measurement of singlet oxygen ((1)O2). Catalyzing conversion of H2O2 into (1)O2 by pPIX was monitored in vitro under varied H2O2 content, temperature, and PH value in the reaction. Ex vivo mitochondrial model was used to analyze effects of ferrochelatase (FECH) and high energy X-rays on this catalytic reaction.
  
  
  RESULTS
  In complete dark, measurable (1)O2 was generated when 1.5 mM of H2O2 was incubated with 24 μM of pPIX H2O2 at 37°C for 3 hours. Mitochondrial yield of H2O2 was 0.11±0.03 nmole/mg/min. Mitochondrial FECH significantly improve the catalytic ability of pPIX converting H2O2 into (1)O2. At presence of high-energy X-ray, incubation of 14.4 μM of pPIX with 0.54 μM of H2O2 also generated (1)O2, during which the fluorescence density of 1.05 μM of DMA decreased by 41.5% (P < 0.05). This conversion was not observed when pPIX was replaced with structurally similar hematoporphyrin.
  
  
  CONCLUSIONS
  pPIX can catalyze conversion of H2O2 into (1)O2.
authors.affiliation: Beijing Big Base (Top Grade) Equipment Co., LTD China ; Wuxi Yiren Cancer Hospital China.
authors.forename: Jun
authors.initials: J
authors.lastname: Zeng
authors.affiliation: Beijing Big Base (Top Grade) Equipment Co., LTD China.
authors.forename: Qiyin
authors.initials: Q
authors.lastname: Sun
authors.affiliation: Foundation Lab, Wuxi Yiren Cancer Hospital China.
authors.forename: Jihui
authors.initials: J
authors.lastname: Su
authors.affiliation: Foundation Lab, Wuxi Yiren Cancer Hospital China.
authors.forename: Jihui
authors.initials: J
authors.lastname: Han
authors.affiliation: Beijing Big Base (Top Grade) Equipment Co., LTD China.
authors.forename: Quanshi
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Radiation Therapy Center, Wuxi Yiren Cancer Hospital China.
authors.forename: Yuehui
authors.initials: Y
authors.lastname: Jin
keywords: Protoporphyrin; catalysis; singlet oxygen