Albumin (Human serum albumin) (HSA)

Albumin is the most abundant plasma protein produced mainly by hepatocytes, with a concentration around 600 μM in healthy humans. Its heart-shaped structure consists of three domains, each divided into two subdomains. Albumin binds a wide variety of endogenous and exogenous molecules at defined sites, notably Sudlow Site I (subdomain IIA) and II (IIIA), and others. Albumin also demonstrates pseudoesterase and true esterase enzymatic activities at specific tyrosine residues. Its pivotal biological roles include maintaining oncotic pressure, serving as the main antioxidant in plasma via its free Cys-34 thiol group, transporting multiple drugs and molecules, and acting as a negative acute-phase reactant in inflammation. Albumin synthesis is regulated by nutritional status, growth hormones, and pro-inflammatory cytokines, whereas its degradation and recycling are tightly regulated by the neonatal Fc receptor (FcRn) and specific albumin receptors like GP60 (native) and GP18/GP30 (modified). Albumin undergoes various post-translational modifications (oxidation, glycation, nitrosylation), which can alter its structure, ligand binding properties, and biological functions, impacting its status as a biomarker and affecting clinical outcomes in a range of diseases.

Other names

Human serum albuminSerum albuminHSAAlbumin

Binding to albumin modifies the free (active) concentration of drugs, affecting pharmacokinetics, half-life, and distribution Ligand binding at Sudlow Sites I and II (primary drug binding pockets of HSA) Displacement interactions: some drugs can displace other ligands, altering efficacy and toxicity