Equine serum albumin (ESA)

Equine serum albumin is the principal plasma protein of horses (Equus caballus), belonging to the serum albumin family. It is a large, globular, heart-shaped protein comprised mainly of alpha-helices, organized into three major domains, each of which is further divided into subdomains[1][6][7]. ESA functions mainly as a multipurpose transport protein for small molecules, including hormones, fatty acids, drugs, and metal ions, and plays a fundamental role in regulating blood oncotic pressure and pH[6][7]. Its ligand-binding pockets can interact with a remarkably wide range of compounds, and structural studies show significant homology and structural similarity to albumins from other mammals, such as human (HSA), bovine (BSA), and rabbit (LSA)[1][3][5][7]. ESA is widely employed as a research model for protein chemistry, drug-binding studies, and immunology. While it is not a human therapeutic target, its properties are essential for its functions as a biological carrier and allergen[3][4]. ESA itself does not play a direct role in human disease; however, cross-species albumins are important in understanding immunogenicity and allergy[4].

Other names

Horse serum albuminESAAlbumin (when referring to Equus caballus source specifically)

Drug sequestration and transport: By binding drugs in blood, ESA influences their free concentration, distribution, and pharmacokinetics. Ligand binding at defined pockets, usually involving hydrophobic interactions and, at times, metal ion coordination.