Conversion of 24-methylcholesterol to 6-oxo-24-methylcholestanol, a putative intermediate of the biosynthesis of brassinosteroids, in cultured cells of Catharanthus roseus

Suzuki, Hiroyuki; Inoue, T.; Fujioka, Shozo; Saito, Tamio; Takatsuto, Suguru; Yokota, Takao; Murofushi, Noboru; Yanagisawa, Tadashi; Sakurai, Akira

doi:10.1016/0031-9422(95)00579-v

Cited by 51 publications

(20 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…So far no evidence for the conversion of 6-DeoxoTY to TY has been obtained in similar metabolic studies using cultured cells of C. roseus. It has been reported that C6 oxidation occurs to convert CN to 6-OxoCN and 6-DeoxoCS to CS in C. roseus (Suzuki et al, 1995b;Choi et al, 1996). Our present results suggest that C6 oxidation may occur in several other steps.…”

Section: New Branched Pathway: 6-deoxoty To Tysupporting

confidence: 52%

Biosynthetic Pathways of Brassinolide in Arabidopsis

et al. 2000

Self Cite

View full text Add to dashboard Cite

Our previous studies on the endogenous brassinosteroids (BRs) in Arabidopsis have provided suggestive evidence for the operation of the early C6-oxidation and the late C6-oxidation pathways, leading to brassinolide (BL) in Arabidopsis. However, to date the in vivo operation of these pathways has not been fully confirmed in this species. This paper describes metabolic studies using deuterium-labeled BRs in wild-type and BR-insensitive mutant (bri1) seedlings to establish the intermediates of the biosynthetic pathway of BL in Arabidopsis. The first evidence for the conversion of campestanol to 6-deoxocathasterone and the conversion of 6-deoxocathasterone to 6-deoxoteasterone is provided. The later biosynthetic steps (6-deoxoteasterone 3 3-dehydro-6-deoxoteasterone 3 6-deoxotyphasterol 3 6-deoxocastasterone 3 6␣-hydroxycastasterone 3 castasterone 3 BL) were demonstrated by stepwise metabolic experiments. Therefore, these studies complete the documentation of the late C6-oxidation pathway. The biosynthetic sequence involved in the early C6-oxidation pathway (teasterone 3 3-dehydroteasterone 3 typhasterol 3 castasterone 3 BL) was also demonstrated. These results show that both the early and late C6-oxidation pathways are functional in Arabidopsis. In addition we report two new observations: the presence of a new branch in the pathway, C6 oxidation of 6-deoxotyphasterol to typhasterol, and increased metabolic flow in BR-insensitive mutants.

show abstract

Section: New Branched Pathway: 6-deoxoty To Tysupporting

confidence: 52%

Biosynthetic Pathways of Brassinolide in Arabidopsis

et al. 2000

Self Cite

View full text Add to dashboard Cite

show abstract

“…Yeasts transformed with AtBR6ox and Dwarf could not catalyze C-6 oxidation of [ 2 H 6 ]6-DeoxoCT and [ 2 H 6 ]CN (Tables I and II Suzuki et al, 1995). We recently found the natural occurrence of 6-OxoCN in Arabidopsis (S. Fujioka, unpublished data), which may suggest that an unknown BR-6-oxidase catalyzing CN to 6-OxoCN exists in Arabidopsis.…”

Section: Discussionmentioning

confidence: 97%

Brassinosteroid-6-Oxidases from Arabidopsis and Tomato Catalyze Multiple C-6 Oxidations in Brassinosteroid Biosynthesis

et al. 2001

Self Cite

View full text Add to dashboard Cite

Brassinosteroids (BRs) are steroidal plant hormones that are essential for growth and development. It has been proposed that BRs are synthesized via two parallel pathways, the early and late C-6 oxidation pathways according to the C-6 oxidation status. The tomato (Lycopersicon esculentum) Dwarf gene encodes a cytochrome P450 that has been shown to catalyze the C-6 oxidation of 6-deoxocastasterone to castasterone. We isolated an Arabidopsis ortholog (AtBR6ox gene) of the tomato Dwarf gene. The encoded polypeptide has characteristics of P450s and is classified into the CYP85 family. The AtBR6ox and tomato Dwarf gene were expressed in yeast and the ability of the transformed yeast cells to metabolize 6-deoxo-BRs was tested. Metabolites were analyzed by gas chromatography-mass spectrometry. Both enzymes catalyze multiple steps in BR biosynthesis: 6-deoxoteasterone to teasterone, 3-dehydro-6-deoxoteasterone to 3-dehydroteasterone, 6-deoxotyphasterol to typhasterol, and 6-deoxocastasterone to castasterone. Our results indicate that the AtBR6ox gene and the tomato Dwarf gene encode steroid-6-oxidases and that these enzymes have a broad substrate specificity. This suggests that the BR biosynthetic pathway consists of a metabolic grid rather than two separate parallel pathways.

show abstract

“…Previously, Suzuki et al (1995) examined metabolism of 13 C-and/or 14 C-labeled campesterol in cultured cells of C. roseus. In their study a major metabolite of campesterol was identified to be campestanol.…”

Section: Metabolism Of 2 H-labeled Intermediates Involved In the Formmentioning

confidence: 99%

Arabidopsis det2 Is Defective in the Conversion of (24R)-24-Methylcholest-4-En-3-One to (24R)-24-Methyl-5α-Cholestan-3-One in Brassinosteroid Biosynthesis1

et al. 1999

Self Cite

View full text Add to dashboard Cite

Previously, we have shown that the Arabidopsis det2 (deetiolated2) mutant is defective in the biosynthesis of brassinosteroids (BR) and that DET2 (a steroid 5␣-reductase) acts early in the proposed BR biosynthetic pathway. In this paper we present further biochemical characterization of det2. We have undertaken metabolic experiments with 2 H-labeled substrates of intermediates involved in the formation of campestanol from campesterol, and quantitative analysis of intermediates in Arabidopsis wild type and det2. The results of these studies indicate the early operating steps of BR biosynthesis as: campesterol 3 4-en-3␤-ol 3 4-en-3-one 3 3-one 3 campestanol in Arabidopsis, with det2 deficient in the conversion of 4-en-3-one to 3-one. We have also detected these intermediates in the formation of campestanol from campesterol and their metabolic conversions using cultured cells of Catharanthus roseus. These studies confirmed the biosynthetic sequence of events from campesterol to campestanol as was found in Arabidopsis. As such, the originally proposed biosynthetic pathway should be modified.

show abstract

Conversion of 24-methylcholesterol to 6-oxo-24-methylcholestanol, a putative intermediate of the biosynthesis of brassinosteroids, in cultured cells of Catharanthus roseus

Cited by 51 publications

References 27 publications

Biosynthetic Pathways of Brassinolide in Arabidopsis

Biosynthetic Pathways of Brassinolide in Arabidopsis

Brassinosteroid-6-Oxidases from Arabidopsis and Tomato Catalyze Multiple C-6 Oxidations in Brassinosteroid Biosynthesis

Arabidopsis det2 Is Defective in the Conversion of (24R)-24-Methylcholest-4-En-3-One to (24R)-24-Methyl-5α-Cholestan-3-One in Brassinosteroid Biosynthesis1

Contact Info

Product

Resources

About