Characterization of an inducible P450 hydroxylase involved in the rice diterpene phytoalexin biosynthetic pathway

Arch Biochem Biophys. 1995 Feb 1;316(2):707-12. doi: 10.1006/abbi.1995.1094.


Ent-isopimara-8(14),15-dien-3 beta-ol (1) was isolated from uv-irradiated rice (Oryza sativa L.) leaves. Since 1 was converted to the rice diterpene phytoalexins and oryzalexins D (ent-isopimara-8(14),15-diene-3 beta,7 alpha-diol) and E (ent-isopimara-8(14),15-diene-3 beta,9 alpha-diol) in uv-irradiated rice leaf microsome fraction in the presence of oxygen and NADPH, it was concluded that 1 was the biosynthetic precursor of these oryzalexins. This enzyme reaction was inhibited by cytochrome P450 inhibitors such as piperonyl butoxide, SKF-525A, paclobutorazole, metyrapone, cytochrome c, and carbon monoxide. The lack of inhibitory activity of 1 for spore germination of Pyricularia oryzae indicates that the final cytochrome P450-dependent hydroxylation steps in converting 1 to oryzalexins D and E are essential for the production of rice phytoalexins with antifungal activities.

MeSH terms

  • Antifungal Agents / metabolism*
  • Antifungal Agents / pharmacology
  • Cytochrome P-450 Enzyme Inhibitors
  • Diterpenes / chemistry
  • Diterpenes / metabolism*
  • Diterpenes / pharmacology
  • Mixed Function Oxygenases / metabolism*
  • Oryza / enzymology*
  • Oryza / radiation effects
  • Plant Extracts / biosynthesis*
  • Plant Extracts / pharmacology
  • Sesquiterpenes
  • Spores, Fungal / drug effects
  • Terpenes
  • Ultraviolet Rays


  • Antifungal Agents
  • Cytochrome P-450 Enzyme Inhibitors
  • Diterpenes
  • Plant Extracts
  • Sesquiterpenes
  • Terpenes
  • isopimara-8(14),15-dien-3-ol
  • phytoalexins
  • Mixed Function Oxygenases