Arabidopsis CYP85A2 catalyzes lactonization reactions in the biosynthesis of 2-deoxy-7-oxalactone brassinosteroids

Biosci Biotechnol Biochem. 2008 Aug;72(8):2110-7. doi: 10.1271/bbb.80192. Epub 2008 Aug 7.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / enzymology*
  • Arabidopsis / genetics
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Catalysis
  • Cytochrome P-450 Enzyme System / genetics
  • Cytochrome P-450 Enzyme System / metabolism*
  • Gas Chromatography-Mass Spectrometry
  • Lactones / chemistry*
  • Molecular Structure
  • Pichia / genetics
  • Pichia / metabolism
  • Proto-Oncogene Proteins c-myb / genetics
  • Proto-Oncogene Proteins c-myb / metabolism
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Steroids / biosynthesis*
  • Steroids / chemistry*
  • Transgenes / genetics


  • ATR1 protein, Arabidopsis
  • Arabidopsis Proteins
  • Lactones
  • Proto-Oncogene Proteins c-myb
  • Recombinant Proteins
  • Steroids
  • Cytochrome P-450 Enzyme System
  • brassinosteroid-6 oxidase 2, Arabidopsis