Mucin glycoprotein disulfide bonds

Mucin glycoprotein disulfide bonds are the critical covalent cross-links that maintain the three-dimensional gel matrix of airway mucus. These bonds primarily occur between the cysteine-rich amino- and carboxy-terminal domains of large secreted polymeric mucins, specifically MUC5AC and MUC5B (Thornton et al., 2008). In healthy airways, this network provides the necessary viscoelastic properties for effective mucociliary clearance; however, in diseases like cystic fibrosis and chronic obstructive pulmonary disease (COPD), excessive cross-linking results in highly viscous mucus that obstructs the airways (Fahy & Dickey, 2010). Classic mucolytic drugs, such as N-acetylcysteine, target these bonds by acting as reducing agents that break the disulfide bridges through thiol-disulfide exchange (Bonser & Erle, 2017). This chemical reduction decreases the molecular weight of the mucin polymers, significantly lowering mucus viscosity and facilitating its removal from the respiratory tract. Beyond simple reduction, the state of these bonds is also influenced by the local redox environment and pH of the airway surface liquid (Yuan et al., 2015). Targeting these structural bonds remains a cornerstone of therapy for managing mucus hypersecretion and improving pulmonary function in chronic respiratory conditions.

Other names

Mucin disulfide bridgesIntermolecular disulfide cross-linksMucin thiol-disulfide bondsMucin S-S bonds

Reduction of intermolecular disulfide bonds via thiol-disulfide exchange, leading to the depolymerization of mucin glycoproteins and decreased mucus viscosity.