brassinosteroid biosynthetic process

Definition

Target type: biologicalprocess

The chemical reactions and pathways resulting in the formation of brassinosteroids, any of a group of steroid derivatives that occur at very low concentrations in plant tissues and may have hormone-like effects. [ISBN:0192801023]

The brassinosteroid biosynthetic process is a complex pathway that involves the conversion of campesterol, a sterol precursor, into active brassinosteroids. These hormones play crucial roles in plant growth and development, regulating processes such as cell elongation, division, differentiation, and vascular tissue formation. The pathway consists of multiple enzymatic steps, each catalyzed by specific enzymes, and can be broadly divided into three stages:

1. **Early Steps**: The biosynthesis begins with the conversion of campesterol to 24-methylenecholesterol. This step is catalyzed by the enzyme C-24 sterol methyltransferase (SMT). Subsequently, 24-methylenecholesterol is converted to campestanol by the enzyme sterol reductase.
2. **Intermediate Steps**: This stage involves the formation of brassinosteroid precursors, such as 24-epibrassinolide. These precursors are synthesized through a series of oxidation and hydroxylation reactions catalyzed by cytochrome P450 enzymes. Key enzymes involved include CYP90B1, CYP85A1, and CYP85A2.
3. **Late Steps**: The final steps in the pathway involve the synthesis of bioactive brassinosteroids, including brassinolide and castasterone. This stage is characterized by the formation of a 6-keto group and a 7-oxo group on the steroid nucleus, a process catalyzed by the enzyme DWF4, a 2-oxoglutarate-dependent dioxygenase.

The brassinosteroid biosynthetic process is highly regulated and influenced by various environmental factors, such as light, temperature, and stress. This complex pathway ensures the precise control of brassinosteroid levels, ensuring optimal plant growth and development.'
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Proteins (1)

Compounds (2)