Mature human afamin, the product of the AFM gene, is a single chain 75 kDa protein consisting of 578 amino acid residues. It contains three consecutive albumin domains (aa 36–206, 211–403 and 404–599) that contain characteristic 5 or 6 intra-chain disulfide bonds. AFM is a member of the albumin gene family, which is comprised of four genes that localize to chromosome 4 in a tandem arrangement. These four genes encode structurally related serum transport proteins that are known to be evolutionarily related. The glycoprotein afamin is located on chromosome 4q11–q13 in humans. Afamin is predominantly expressed in the liver and secreted into the bloodstream; minor expressions have been described also in human brain [2], heart, kidney, testis and ovary. Afamin has been reported to bind vitamin E, especially α-tocopherol and γ-tocopherol, two of the most important forms of vitamin E, in vitro and in vivo and to possess multiple binding sites for both tocopherol isomers. Comparative proteomics has previously identified afamin as a potential biomarker for ovarian cancer. Patients with ovarian cancer displayed significantly decreased plasma concentrations of afamin by comparison to healthy controls and, very recently, extended by showing significant associations between afamin plasma concentrations and clinical outcomes (response to therapy and survival rates) were reported. Human plasma afamin is reported to be strongly associated with criteria for metabolic syndrome. Data from a prospective study design as well as corresponding data from afamin-transgenic mice suggest an active role of afamin in the development of metabolic syndrome [7]. In patients with polycystic ovary syndrome, afamin might serve as a discriminatory predictive parameter of insulin resistance and metabolic syndrome.
- References to Afamin (AFM, α-1T-glycoprotein)