sialyltransferase activity

Definition

Target type: molecularfunction

Catalysis of the transfer of sialic acid to an acceptor molecule, typically the terminal portions of the sialylated glycolipids (gangliosides) or to the N- or O-linked sugar chains of glycoproteins. [GOC:cjm, PMID:26192491]

Sialyltransferases are a family of glycosyltransferases that catalyze the transfer of sialic acid (also known as N-acetylneuraminic acid) from a donor molecule, typically CMP-sialic acid, to a specific acceptor molecule, usually a carbohydrate chain. This process, known as sialylation, is a crucial step in the biosynthesis of glycoconjugates, including glycoproteins, glycolipids, and oligosaccharides.

Sialyltransferases are highly specific in their substrate recognition. They often exhibit a strict preference for both the donor molecule and the acceptor molecule, including the specific sugar residue to which the sialic acid is added. This specificity is determined by the amino acid sequence of the enzyme, particularly in the catalytic site and the carbohydrate-binding domain.

The primary molecular function of sialyltransferases is to modify the structure and properties of glycoconjugates. By attaching sialic acid, these enzymes can:

* **Alter the charge of the glycoconjugate:** Sialic acid is a negatively charged sugar, and its addition can significantly affect the overall charge of the molecule. This can influence its interactions with other molecules, such as proteins or other carbohydrates.
* **Modulate the biological activity of the glycoconjugate:** Sialylation can affect the function of glycoproteins, glycolipids, and oligosaccharides in various ways, including cell adhesion, signaling, and immune recognition.
* **Increase the stability and solubility of the glycoconjugate:** Sialylation can enhance the stability and solubility of glycoconjugates, particularly in aqueous environments.

Sialyltransferases play diverse roles in various biological processes, including:

* **Cell adhesion:** Sialylated glycoconjugates on the cell surface are involved in cell-cell interactions and cell adhesion.
* **Signaling pathways:** Sialylation can regulate the activity of signaling molecules, including growth factors and chemokines.
* **Immune recognition:** Sialylated glycoconjugates on the cell surface can act as recognition markers for the immune system, modulating immune responses.
* **Development and differentiation:** Sialylation is crucial for the development and differentiation of various tissues and organs.

Dysregulation of sialyltransferase activity can lead to various diseases, including cancer, inflammatory disorders, and neurodevelopmental disorders. Therefore, understanding the molecular function of sialyltransferases is essential for developing new therapeutic approaches for these diseases.'
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Proteins (4)

Compounds (12)