Human serum albumin Cys34 (HSA Cys34)

The Cys34 residue of human serum albumin (HSA) is the only free cysteine within the protein, located in domain I of the molecule[3][4][7]. This free thiol confers major antioxidant activity to albumin, accounting for the majority of plasma's SH (sulfhydryl) groups, and is a key scavenger of reactive oxygen and nitrogen species[1][3][4][6]. Under physiological and pathological conditions, Cys34 can be reversibly or irreversibly oxidized, forming mixed disulfides, sulfinic and sulfonic acids, and, less commonly, other modifications such as sulfinamides[2][5][6]. The redox state of Cys34 modulates albumin's conformation and its ability to bind drugs and endogenous ligands at sites I and II[1][4]. Increased cysteinylation or oxidation of Cys34 is observed in various diseases characterized by oxidative stress, such as chronic liver and kidney disease, diabetes, and cardiovascular disease[1][4][5][6]. Such modifications compromise albumin's antioxidant capacity and affect ligand binding, contributing to disease progression and serving as sensitive biomarkers of systemic oxidative stress[1][4][5]. Cys34 itself is not a direct therapeutic target, but its chemical forms are clinically relevant diagnostic indicators.

Other names

Albumin Cys34 residueCys34 of human serum albuminHSA Cys34Free thiol on albumin