Human serum albumin (HSA) Cysteine-34 (HSA (Cys34))

Human serum albumin (HSA) is the most abundant protein in human plasma, and its Cysteine-34 (Cys34) residue is the only free thiol group among its 35 cysteine residues (UniProt P02768). This specific residue serves as the primary extracellular antioxidant, accounting for approximately 80% of the thiol-based radical scavenging capacity in the blood (PubMed: 18482394). Under physiological conditions, Cys34 exists mostly in a reduced state known as human mercaptalbumin (HMA), but it is susceptible to oxidation to human non-mercaptalbumin (HNA) during systemic inflammation or oxidative stress (PubMed: 25503335). Beyond its redox role, Cys34 is a key site for the covalent attachment of drugs, particularly those designed for long-circulating prodrug delivery systems like Aldoxorubicin (PubMed: 24138310). It also interacts with metal-based therapeutics such as cisplatin and gold-based drugs, significantly influencing the pharmacokinetics and toxicity profiles of various pharmacological agents (PubMed: 22403074).

Other names

AlbuminSerum albuminCys34MercaptalbuminHuman mercaptalbuminHuman non-mercaptalbuminHMAHNA

Covalent conjugation to the free thiol group, thiol-disulfide exchange, and scavenging of reactive oxygen and nitrogen species.