Target type: biologicalprocess
A protein modification process that results in the addition of a sialic acid unit to the end of an oligosaccharide chain in a glycoprotein. [PMID:21930713]
Sialylation is a crucial post-translational modification in which sialic acids, negatively charged monosaccharides, are attached to the terminal ends of oligosaccharide chains on glycoproteins and glycolipids. This process occurs in the Golgi apparatus, a cellular organelle responsible for protein sorting and modification.
The enzyme responsible for sialylation is sialyltransferase, a glycosyltransferase that catalyzes the transfer of sialic acid from a donor substrate, typically CMP-sialic acid, to an acceptor substrate, the oligosaccharide chain. There are multiple sialyltransferase isoforms, each with distinct substrate specificities and tissue distributions, contributing to the diversity of sialylation patterns observed in various glycoconjugates.
The process of sialylation involves several steps:
1. **Synthesis of CMP-sialic acid:** Sialic acid is synthesized from N-acetylmannosamine and pyruvate, and then activated by the enzyme CMP-sialic acid synthetase, generating CMP-sialic acid, the donor substrate for sialyltransferases.
2. **Transport of CMP-sialic acid to the Golgi:** CMP-sialic acid is transported from the cytoplasm to the Golgi lumen, where sialyltransferases reside.
3. **Recognition and binding of the acceptor substrate:** Sialyltransferases recognize and bind to specific oligosaccharide structures on the acceptor substrate, typically a terminal galactose or N-acetylglucosamine residue.
4. **Transfer of sialic acid:** The sialyltransferase catalyzes the transfer of sialic acid from CMP-sialic acid to the acceptor substrate, forming a glycosidic linkage between the sialic acid and the oligosaccharide chain.
5. **Regulation of sialylation:** Sialylation is tightly regulated, with the activity of sialyltransferases influenced by factors such as cell type, developmental stage, and environmental stimuli.
Sialylation plays a significant role in various biological processes, including:
* **Cell adhesion and recognition:** Sialic acids contribute to the recognition and binding of cells to each other and to extracellular matrix components.
* **Immune regulation:** Sialylation influences the interaction of cells with the immune system, affecting the recognition of pathogens and the activation of immune cells.
* **Signal transduction:** Sialylation can alter the function of glycoproteins involved in signal transduction pathways.
* **Stability and protection:** Sialylation contributes to the stability and protection of glycoproteins against degradation.
Defects in sialylation can lead to various human diseases, including neurological disorders, immunodeficiency, and metabolic diseases. Understanding the intricate process of sialylation is crucial for unraveling the complexity of glycobiology and its role in human health and disease.'
"
Protein | Definition | Taxonomy |
---|---|---|
CMP-N-acetylneuraminate-beta-galactosamide-alpha-2,3-sialyltransferase 1 | A CMP-N-acetylneuraminate-beta-galactosamide-alpha-2,3-sialyltransferase 1 that is encoded in the genome of human. [PRO:DNx, UniProtKB:Q11201] | Homo sapiens (human) |
Compound | Definition | Classes | Roles |
---|---|---|---|
2,3-dihydroxybenzoic acid | 2,3-dihydroxybenzoic acid : A dihydroxybenzoic acid that is benzoic acid substituted by hydroxy groups at positions 2 and 3. It occurs naturally in Phyllanthus acidus and in the aquatic fern Salvinia molesta. 2,3-dihydroxybenzoic acid: RN given refers to parent cpd dihydroxybenzoic acid : Any member of the class of hydroxybenzoic acids carrying two phenolic hydroxy groups on the benzene ring and its derivatives. | dihydroxybenzoic acid | human xenobiotic metabolite; plant metabolite |
protocatechuic acid | 3,4-dihydroxybenzoic acid : A dihydroxybenzoic acid in which the hydroxy groups are located at positions 3 and 4. protocatechuic acid: RN given refers to parent cpd; structure | catechols; dihydroxybenzoic acid | antineoplastic agent; EC 1.1.1.25 (shikimate dehydrogenase) inhibitor; EC 1.14.11.2 (procollagen-proline dioxygenase) inhibitor; human xenobiotic metabolite; plant metabolite |
gallic acid | gallate : A trihydroxybenzoate that is the conjugate base of gallic acid. | trihydroxybenzoic acid | antineoplastic agent; antioxidant; apoptosis inducer; astringent; cyclooxygenase 2 inhibitor; EC 1.13.11.33 (arachidonate 15-lipoxygenase) inhibitor; geroprotector; human xenobiotic metabolite; plant metabolite |
beta-resorcylic acid | beta-resorcylic acid: RN given refers to parent cpd; structure | ||
2,5-dihydroxybenzoic acid | 2,5-dihydroxybenzoic acid : A dihydroxybenzoic acid having the two hydroxy groups at the 2- and 5-positions. 2,5-dihydroxybenzoic acid: RN given refers to parent cpd; a oxidative product of saligenin | dihydroxybenzoic acid | EC 1.13.11.33 (arachidonate 15-lipoxygenase) inhibitor; fungal metabolite; human metabolite; MALDI matrix material; mouse metabolite |
veratric acid | 3,4-dimethoxybenzoic acid : A member of the class of benzoic acids that is benzoic acid substituted by methoxy groups at positions 2 and 3. veratric acid: RN given refers to parent cpd; structure | benzoic acids | allergen; plant metabolite |
methyl gallate | methyl 3,4,5-trihydroxybenzoate : A gallate ester obtained by the formal condensation of gallic acid with methanol. It exhibits anti-oxidant, anti-tumor, anti-microbial and anti-inflammatory properties. methyl gallate: has both immunosuppressive and phytogenic antineoplastic activities; isolated from Acer saccharinum | gallate ester | anti-inflammatory agent; antioxidant; plant metabolite |
3,4,5-trimethoxybenzoic acid | 3,4,5-trimethoxybenzoic acid : A benzoic acid derivative carrying 3-, 4- and 5-methoxy substituents. 3,4,5-trimethoxybenzoic acid: RN given refers to parent cpd; structure | benzoic acids; methoxybenzenes | human urinary metabolite; human xenobiotic metabolite; plant metabolite |
syringic acid | syringic acid : A dimethoxybenzene that is 3,5-dimethyl ether derivative of gallic acid. syringic acid: RN given refers to parent cpd; structure in third source | benzoic acids; dimethoxybenzene; phenols | plant metabolite |
epigallocatechin gallate | (-)-epigallocatechin 3-gallate : A gallate ester obtained by the formal condensation of gallic acid with the (3R)-hydroxy group of (-)-epigallocatechin. epigallocatechin gallate: a steroid 5alpha-reductase inhibitor and antimutagen in green tea (Camellia sinensis) | flavans; gallate ester; polyphenol | antineoplastic agent; antioxidant; apoptosis inducer; geroprotector; Hsp90 inhibitor; neuroprotective agent; plant metabolite |
guanosine diphosphate | Guanosine Diphosphate: A guanine nucleotide containing two phosphate groups esterified to the sugar moiety. | guanosine 5'-phosphate; purine ribonucleoside 5'-diphosphate | Escherichia coli metabolite; mouse metabolite; uncoupling protein inhibitor |