putrescine biosynthetic process from ornithine

Definition

Target type: biologicalprocess

The chemical reactions and pathways resulting in the formation of putrescine, 1,4-diaminobutane by decarboxylation of ornithine. [GOC:mah, MetaCyc:PWY-46]

Putrescine biosynthesis from ornithine is a crucial step in the polyamine metabolic pathway, essential for numerous cellular functions, including cell growth, differentiation, and response to stress. This process involves the decarboxylation of ornithine, a non-protein amino acid, into putrescine, a diamine.

The reaction is catalyzed by the enzyme ornithine decarboxylase (ODC), a pyridoxal phosphate-dependent enzyme that removes the carboxyl group from ornithine. ODC is highly regulated, and its activity is tightly controlled by various factors, including hormones, growth factors, and cellular stress.

The conversion of ornithine to putrescine occurs in two steps:

1. **Binding of ornithine to ODC**: Ornithine binds to the active site of ODC, forming a Schiff base with the pyridoxal phosphate cofactor.
2. **Decarboxylation**: The carbon-carbon bond between the carboxyl group and the alpha-carbon of ornithine is cleaved, releasing carbon dioxide and forming putrescine.

The putrescine produced in this process serves as a precursor for the synthesis of other polyamines, such as spermidine and spermine. These polyamines play vital roles in cellular processes, including:

* **Regulation of gene expression**: Polyamines can bind to DNA and influence the activity of transcription factors, thereby regulating gene expression.
* **Protein synthesis**: Polyamines are essential for the initiation and elongation of protein synthesis.
* **Cell growth and proliferation**: Polyamines promote cell growth and proliferation by stimulating DNA replication and cell division.
* **Stress response**: Polyamines protect cells from various stresses, including oxidative stress and DNA damage.

Dysregulation of putrescine biosynthesis and polyamine metabolism has been implicated in various diseases, including cancer, cardiovascular disease, and neurodegenerative disorders. Therefore, understanding the intricate mechanisms of putrescine biosynthesis from ornithine is crucial for developing therapeutic strategies for these diseases.
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Proteins (1)

Compounds (4)