title: Arabidopsis CYP85A2 catalyzes lactonization reactions in the biosynthesis of 2-deoxy-7-oxalactone brassinosteroids.
abstract: Brassinolide (BL), a plant 7-oxalactone-type steroid hormone, is one of the active brassinosteroids (BRs) that regulates plant growth and development. BL is biosynthesized from castasterone by the cytochrome P450 monooxygenase, CYP85A2. We showed that a Pichia pastoris transformant that synchronously expresses Arabidopsis P450 reductase gene ATR1 and P450 gene CYP85A2 converts teasterone and typhasterol to 7-oxateasterone and 7-oxatyphasterol, respectively. Thus, CYP85A2 catalyzes the lactonization reactions of not only castasterone but also teasterone and typhasterol. The two 2-deoxy-7-oxalactone-type BRs were identified in Arabidopsis plants. Although the reversible conversion between 7-oxateasterone and 7-oxatyphasterol was observed in vivo, no conversion of 7-oxatyphasterol to BL was observed. The biological activity of 7-oxatyphasterol toward Arabidopsis hypocotyl elongation was nearly the same as that of castasterone. These results suggest that a new BR biosynthetic pathway, a BR lactonization pathway, functions in Arabidopsis and plays an important role in regulating the concentration of active BRs, even though the metabolism of 7-oxatyphasterol to BL is still unknown.
authors.affiliation: Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Japan.
authors.forename: Takumi
authors.initials: T
authors.lastname: Katsumata
authors.forename: Akiko
authors.initials: A
authors.lastname: Hasegawa
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Fujiwara
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Komatsu
authors.forename: Miho
authors.initials: M
authors.lastname: Notomi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Abe
authors.forename: Masahiro
authors.initials: M
authors.lastname: Natsume
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kawaide
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002384:Catalysis; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D007783:Lactones / Q000737:chemistry*; D015394:Molecular Structure; D010843:Pichia / Q000235:genetics / Q000378:metabolism; D020598:Proto-Oncogene Proteins c-myb / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013256:Steroids / Q000096:biosynthesis* / Q000737:chemistry*; D019076:Transgenes / Q000235:genetics
chemical_list: C511988:ATR1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D007783:Lactones; D020598:Proto-Oncogene Proteins c-myb; D011994:Recombinant Proteins; D013256:Steroids; D003577:Cytochrome P-450 Enzyme System; C474079:brassinosteroid-6 oxidase 2, Arabidopsis