If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Synonyms: brassinosteroid biosynthesis - C-22 oxidation branch
|Superclasses:||Biosynthesis → Hormones Biosynthesis → Plant Hormones Biosynthesis → Brassinosteroids Biosynthesis|
Some taxa known to possess this pathway include : Arabidopsis thaliana col
Expected Taxonomic Range: Embryophyta
Brassinosteroids are steroidal hormones that regulate the growth and development of plants. Brassinosteroids are C27, C28 and C29 steroids depending on their C-24 alkyl substituents. More than 50 free, naturally occurring brassinosteroids have been identified in plants, of which brassinolide (BL) is the most biologically active C28, and together with its C28 congeners, is distributed widely in the plant kingdom [Clouse98]. The biosynthesis pathway of brassinolide was initially elucidated using cultured Catharanthus roseus cells. Extensive metabolic studies suggested parallel-branched brassinolide pathways, namely the early and late C-6 oxidation pathways [Fujioka03]. It has been proposed that the late C-6 oxidation pathway plays a predominant role in the light, whereas the early C-6 oxidation pathway is dominant in the dark (see brassinosteroid biosynthesis I) [Noguchi00]. Recent studies suggest that there is a crosstalk between these parallel pathways, implying that they are not totally autonomous. The operation of an early C-22 oxidation branch of the brassinosteroid biosynthetic pathway has also been demonstrated [Fujioka02].
The existence of this alternative biosynthesis branch has been postulated from the study of the Arabidopsis thaliana sax1 and det2 mutants. This novel bypass pathway is composed of C22-hydroxylated compounds. The sax1 phenotype could be rescued by application of synthetic 22α-hydroxy-campest-4-en-3-one and 22α-hydroxy-5α-campestan-3-one. These compounds have since been detected in planta [Fujioka02, Choe01]. This C22α-hydroxy pathway seems to be active in the dark as, under those conditions, its compounds can also phenotypically restore dwf4 and det2 [Ephritikhine99].
The Arabidopsis DWF4 which encodes a CYP90B1 monooxygenase was subsequently cloned. In vitro kinetic analysis showed that the Km value for campesterol was 9 times lower than that for campestanol, and that the catalytic efficiency (Kcat/Km) for campesterol was 325 times higher than that for campestanol [Fujita06]. In Arabidopsis seedlings, the concentration of campesterol was found to be 58 times higher than that of campestanol. Taken together it suggests that campesterol is the major substrate of CYP90B1 and that the C-22 hydroxylation branch is the main route of brassinosteroid biosynthesis in plants (at least in Arabidopsis) [Fujita06].
Additional shortcuts by C-23 hydroxylation have also been detected recently [Ohnishi06].
Superpathways: superpathway of C28 brassinosteroid biosynthesis
Unification Links: AraCyc:PWY-2582
Revised 13-Jul-2010 by Zhang P
Choe01: Choe S, Fujioka S, Noguchi T, Takatsuto S, Yoshida S, Feldmann KA (2001). "Overexpression of DWARF4 in the brassinosteroid biosynthetic pathway results in increased vegetative growth and seed yield in Arabidopsis." Plant J 26(6);573-82. PMID: 11489171
Ephritikhine99: Ephritikhine G, Pagant S, Fujioka S, Takatsuto S, Lapous D, Caboche M, Kendrick RE, Barbier-Brygoo H (1999). "The sax1 mutation defines a new locus involved in the brassinosteroid biosynthesis pathway in Arabidopsis thaliana." Plant J 18(3);315-20. PMID: 10377996
Fujita06: Fujita S, Ohnishi T, Watanabe B, Yokota T, Takatsuto S, Fujioka S, Yoshida S, Sakata K, Mizutani M (2006). "Arabidopsis CYP90B1 catalyses the early C-22 hydroxylation of C27, C28 and C29 sterols." Plant J 45(5);765-74. PMID: 16460510
Ohnishi06: Ohnishi T, Szatmari AM, Watanabe B, Fujita S, Bancos S, Koncz C, Lafos M, Shibata K, Yokota T, Sakata K, Szekeres M, Mizutani M (2006). "C-23 hydroxylation by Arabidopsis CYP90C1 and CYP90D1 reveals a novel shortcut in brassinosteroid biosynthesis." Plant Cell 18(11);3275-88. PMID: 17138693
Asami01: Asami T, Mizutani M, Fujioka S, Goda H, Min YK, Shimada Y, Nakano T, Takatsuto S, Matsuyama T, Nagata N, Sakata K, Yoshida S (2001). "Selective interaction of triazole derivatives with DWF4, a cytochrome P450 monooxygenase of the brassinosteroid biosynthetic pathway, correlates with brassinosteroid deficiency in planta." J Biol Chem 276(28);25687-91. PMID: 11319239
Asami03: Asami T, Mizutani M, Shimada Y, Goda H, Kitahata N, Sekimata K, Han SY, Fujioka S, Takatsuto S, Sakata K, Yoshida S (2003). "Triadimefon, a fungicidal triazole-type P450 inhibitor, induces brassinosteroid deficiency-like phenotypes in plants and binds to DWF4 protein in the brassinosteroid biosynthesis pathway." Biochem J 369(Pt 1);71-6. PMID: 12350224
Bancos02: Bancos S, Nomura T, Sato T, Molnar G, Bishop GJ, Koncz C, Yokota T, Nagy F, Szekeres M (2002). "Regulation of transcript levels of the Arabidopsis cytochrome p450 genes involved in brassinosteroid biosynthesis." Plant Physiol 130(1);504-13. PMID: 12226529
Choe98: Choe S, Dilkes BP, Fujioka S, Takatsuto S, Sakurai A, Feldmann KA (1998). "The DWF4 gene of Arabidopsis encodes a cytochrome P450 that mediates multiple 22alpha-hydroxylation steps in brassinosteroid biosynthesis." Plant Cell 1998;10(2);231-43. PMID: 9490746
Choe99: Choe S, Noguchi T, Fujioka S, Takatsuto S, Tissier CP, Gregory BD, Ross AS, Tanaka A, Yoshida S, Tax FE, Feldmann KA (1999). "The Arabidopsis dwf7/ste1 mutant is defective in the delta7 sterol C-5 desaturation step leading to brassinosteroid biosynthesis." Plant Cell 1999;11(2);207-21. PMID: 9927639
Finsterbusch99: Finsterbusch A, Lindemann P, Grimm R, Eckerskorn C, Luckner M (1999). "Delta(5)-3beta-hydroxysteroid dehydrogenase from Digitalis lanata Ehrh. - a multifunctional enzyme in steroid metabolism?." Planta 209(4);478-86. PMID: 10550629
Fujioka97: Fujioka S, Li J, Choi YH, Seto H, Takatsuto S, Noguchi T, Watanabe T, Kuriyama H, Yokota T, Chory J, Sakurai A (1997). "The Arabidopsis deetiolated2 mutant is blocked early in brassinosteroid biosynthesis." Plant Cell 9(11);1951-62. PMID: 9401120
Kim05a: Kim GT, Fujioka S, Kozuka T, Tax FE, Takatsuto S, Yoshida S, Tsukaya H (2005). "CYP90C1 and CYP90D1 are involved in different steps in the brassinosteroid biosynthesis pathway in Arabidopsis thaliana." Plant J 41(5);710-21. PMID: 15703058
Lachance90: Lachance Y, Luu-The V, Labrie C, Simard J, Dumont M, de Launoit Y, Guerin S, Leblanc G, Labrie F (1990). "Characterization of human 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4-isomerase gene and its expression in mammalian cells." J Biol Chem 265(33);20469-75. PMID: 2243100
Noguchi99: Noguchi T, Fujioka S, Takatsuto S, Sakurai A, Yoshida S, Li J, Chory J (1999). "Arabidopsis det2 is defective in the conversion of (24R)-24-methylcholest-4-En-3-one to (24R)-24-methyl-5alpha-cholestan-3-one in brassinosteroid biosynthesis." Plant Physiol 120(3);833-40. PMID: 10398719
Nomura04: Nomura T, Jager CE, Kitasaka Y, Takeuchi K, Fukami M, Yoneyama K, Matsushita Y, Nyunoya H, Takatsuto S, Fujioka S, Smith JJ, Kerckhoffs LH, Reid JB, Yokota T (2004). "Brassinosteroid deficiency due to truncated steroid 5alpha-reductase causes dwarfism in the lk mutant of pea." Plant Physiol 135(4);2220-9. PMID: 15286289
Rheaume91: Rheaume E, Lachance Y, Zhao HF, Breton N, Dumont M, de Launoit Y, Trudel C, Luu-The V, Simard J, Labrie F (1991). "Structure and expression of a new complementary DNA encoding the almost exclusive 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4-isomerase in human adrenals and gonads." Mol Endocrinol 5(8);1147-57. PMID: 1944309
Simard91: Simard J, Melner MH, Breton N, Low KG, Zhao HF, Periman LM, Labrie F (1991). "Characterization of macaque 3 beta-hydroxy-5-ene steroid dehydrogenase/delta 5-delta 4 isomerase: structure and expression in steroidogenic and peripheral tissues in primate." Mol Cell Endocrinol 75(2);101-10. PMID: 2050270
Szekeres96: Szekeres M, Nemeth K, Koncz-Kalman Z, Mathur J, Kauschmann A, Altmann T, Redei GP, Nagy F, Schell J, Koncz C (1996). "Brassinosteroids rescue the deficiency of CYP90, a cytochrome P450, controlling cell elongation and de-etiolation in Arabidopsis." Cell 1996;85(2);171-82. PMID: 8612270
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