cysteine biosynthetic process via cystathionine

Definition

Target type: biologicalprocess

The chemical reactions and pathways resulting in the formation of cysteine, via the intermediate cystathionine. [GOC:go_curators]

Cysteine biosynthesis via cystathionine is a crucial metabolic pathway that synthesizes the amino acid cysteine, an essential component of proteins and a precursor to various biomolecules. The process occurs in two main steps:

**1. Cystathionine Synthesis:**

- Methionine, a sulfur-containing amino acid, is converted to homocysteine through the action of the enzyme methionine adenosyltransferase (MAT).
- Homocysteine then reacts with serine, another amino acid, in a reaction catalyzed by cystathionine β-synthase (CBS) to produce cystathionine. This reaction requires pyridoxal phosphate (PLP), a derivative of vitamin B6, as a cofactor.

**2. Cystathionine Breakdown:**

- Cystathionine is broken down into cysteine and α-ketobutyrate by the enzyme cystathionine γ-lyase (CSE). This reaction also requires PLP as a cofactor.

The cysteine produced through this pathway is utilized for various essential functions, including:

- Protein synthesis
- Redox regulation through the formation of glutathione, a key antioxidant
- Synthesis of taurine, an important neurotransmitter
- Coenzyme A biosynthesis, which plays a vital role in energy metabolism

**Defects in the enzymes involved in this pathway can lead to various genetic disorders, such as:**

- Homocystinuria: Due to defects in CBS, resulting in elevated homocysteine levels in the blood.
- Cystathioninuria: Caused by deficiencies in CSE, leading to increased cystathionine levels.

These disorders can affect various aspects of health, including cardiovascular function, neurological development, and bone metabolism.'
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Proteins (2)

Compounds (18)