Disulfide bonds in mucus and fibrin proteins

Disulfide bonds in mucus and fibrin proteins are critical covalent cross-links formed between the thiol groups of cysteine residues, playing a fundamental role in the polymerization and structural integrity of these extracellular matrices (Thornton et al., 2008). In the respiratory tract, these bonds cross-link mucin glycoproteins, such as MUC5AC and MUC5B, to create a dense viscoelastic gel that traps pathogens and debris; however, in diseases like cystic fibrosis and chronic obstructive pulmonary disease (COPD), excessive disulfide-mediated polymerization leads to pathological mucus plugging (Sadowska, 2012). Similarly, in the hematological system, disulfide bonds are essential for the assembly of fibrinogen and the subsequent stability of the fibrin meshwork during blood clot formation (Lord, 2011). Pharmacological targeting of these bonds primarily involves thiol-based reducing agents, such as N-acetylcysteine (NAC) and erdosteine, which participate in disulfide-sulfhydryl exchange reactions (PubChem). This process cleaves the protein polymers into smaller, less viscous subunits, thereby facilitating the clearance of obstructive mucus from the airways or assisting in the breakdown of fibrin-rich thrombi (NIH). Consequently, these chemical bonds represent a key therapeutic target for improving respiratory function and managing conditions characterized by abnormal protein aggregation or coagulation.

Other names

Disulfide bridgesS-S bondsCystine cross-linksThiol-disulfide exchange sites

Reduction of intermolecular disulfide bonds into free sulfhydryl groups via disulfide-sulfhydryl exchange, leading to the depolymerization of high-molecular-weight glycoproteins and fibrin, thereby decreasing viscosity and structural stability (Sadowska, 2012; Thornton et al., 2008).