Serum albumin, the main protein of plasma, has a good binding capacity for water, Ca(2+), Na(+), K(+), fatty acids, hormones, bilirubin and drugs. Its main function is the regulation of the colloidal osmotic pressure of blood (By similarity). Inhibits trypsin but has no inhibitory effect on thrombin, chymotrypsin, elastase and subtilisin. Plasma. Also expressed in skin (at protein level). Belongs to the ALB/AFP/VDB family.