title: Characterization of an inducible P450 hydroxylase involved in the rice diterpene phytoalexin biosynthetic pathway.
abstract: 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.
authors.affiliation: Laboratory of Bioorganic and Agricultural Chemistry, School of Agriculture, Ibaraki University, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Kato
authors.forename: O
authors.initials: O
authors.lastname: Kodama
authors.forename: T
authors.initials: T
authors.lastname: Akatsuka
mesh_terms: D000935:Antifungal Agents / Q000378:metabolism* / Q000494:pharmacology; D065607:Cytochrome P-450 Enzyme Inhibitors; D004224:Diterpenes / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D012275:Oryza / Q000201:enzymology* / Q000528:radiation effects; D010936:Plant Extracts / Q000096:biosynthesis* / Q000494:pharmacology; D012717:Sesquiterpenes; D013172:Spores, Fungal / Q000187:drug effects; D013729:Terpenes; D014466:Ultraviolet Rays; D000094162:Phytoalexins
chemical_list: D000935:Antifungal Agents; D065607:Cytochrome P-450 Enzyme Inhibitors; D004224:Diterpenes; D010936:Plant Extracts; D012717:Sesquiterpenes; D013729:Terpenes; C092044:isopimara-8(14),15-dien-3-ol; D006899:Mixed Function Oxygenases; D000094162:Phytoalexins