Salivary mucins are well recognized as an important factor in the preservation of the health of the oral cavity. These large glycoproteins play a major role in the formation of protective coatings covering tooth enamel and oral mucosa, which act as a dynamic functional barrier that can modulate the reaction towards detrimental effects of oral environment, hence defending both teeth and oral mucosa.
- two main molecular weight forms:
- MG1 >1000 kDa;
- MG2 200-300 kDa;
both displaying virtually identical carbohydrate chain make-up, ranging in size from 3 to 16 sugar units.
- Lack precise folded structure of globular proteins
- Asymmetrical molecules with open, randomly organized structure
- Polypeptide backbone (apomucin) with CHO side-chains
- Side chains may end in negatively charged groups, such as sialic acid and bound sulfate
- Hydrophillic, entraining water (resists dehydration)
- Unique rheological properties (e.g., high elasticity, adhesiveness, and low solubility)
- Tissue coating
- creates a protective coating about hard and soft tissues
- has a primary role in formation of acquired pellicle
- concentrates anti-microbial molecules at mucosal interface
- Aggregation of bacterial cells
- bacterial adhere to mucins may result in surface attachment, or
- mucin coated bacteria may be unable to attach to the surface
The bacterial aggregating activity of salivary mucins appears to be associated with sulfomucins rather than sialomucins.
Open Question:interaction with surfactant protein D (Lung and Saliva),anti-influenza and anti-HIV activity
While the removal of sialic acid (pathway) causes only partial loss in mucin aggregating capacity, a complete loss in the bacterial aggregating activity occurs following mucin desulfation.
Salivary sulfomucins and sialomucins actively participate in the modulation of the oral mucosal calcium channel activity through the inhibition of EGF-stimulated channel protein tyrosine phosphorylation.
- Bacterial adhesion
- mucin oligosaccharides mimic those on mucosal cell surface
- react with bacterial adhesins blocking them
These functions and the buffer capacity of these mucins may also be involved in the defence against HIV infections in the oral cavity, contrasting trough pH, structure, binding variations the virus' activity.
Open Question: One possibility is that the negative charges on mucins through sialic acid and sulphate groups could be responsible for specific interactions with receptors on the virus. ??
focus on HIV