Fetuin-B

Fetuins are members of the cystatin superfamily of cysteine protease inhibitors. Additional members of this superfamily are kininogen and histidine-rich glycoprotein. Fetuin A and B are two known members of the fetuin family. Hepatocytes are believed to be the principal cellular source, but other cell types also express it. Fetuin A, also known as α2-Heremans-Schmid glycoprotein, is an inhibitor of basic calcium phosphate precipitation and a negative acutephase protein. Normal circulating levels of Fetuin A in adults (300-600 ug/mL) fall significantly (30-50%) during injury and infection. Fetuin A and B display similarities and differences in their characteristics. Fetuin B exhibits reduction of calcification, while both mRNA levels were downregulated during the acute phase in inflammation-induced rats. However, they share only 20% amino acid sequence identity. The amounts of Fetuin B in human serum, unlike Fetuin A, vary with gender and are higher in females than in males.