Hydrogen peroxide dependent N-demethylase activity in the leaves of normal and heat-shocked bean plants

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Formaldehyde producing enzymatic reactions were studied in the cell-free extracts of bean leaves. In the presence of hydrogen peroxide enzymatic N-demethylation was observed using xenobiotic substrates. Marked peroxidase activity which is also capable of producing formaldehyde was detected in the extracts, too. As peroxidase inhibitors strongly inhibited the demethylase activities, the involvement of peroxidases in the demethylation can be supposed. The results suggest that cytochrome P-450s do not contribute to the formaldehyde production observed in the extracts. The temperature and pH dependence of demethylase and peroxidase activities were investigated. The hydrogen peroxide dependent N-demethylase and peroxidase activities in the extracts of heat-shocked beans did not differ significantly from those in control extracts. The increase of formaldehyde level in bean leaves observed after heat shock can be explained by the temperature dependence of the above mentioned activities and by supposing the enhanced hydrogen peroxide formation in the leaves during heat shock. Further studies are needed to identify the enzymes displaying the demethylase activity observed and their physiological substrates.

Original languageEnglish
Pages (from-to)21-27
Number of pages7
JournalPlant Science
Issue number1-2
Publication statusPublished - 1987


  • N-demethylation
  • bean
  • formaldehyde
  • heat shock
  • hydrogen peroxide
  • peroxidase

ASJC Scopus subject areas

  • Genetics
  • Agronomy and Crop Science
  • Plant Science

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