ABSTRACT
Riboflavin-binding protein (RBP) and riboflavin-carrier protein (RCP) have been used to describe proteins that interact with various flavins. Laying hens, and probably other avian species and reptiles, synthesize a form of RfBP in the liver that is secreted into blood, where it complexes with riboflavin and is subsequently taken up by the ovary and deposited in the yolk of developing oocytes. The oviduct also makes RfBP that is incorporated into the albumen, or egg white. In man, flavins are usually absorbed in the form of riboflavin by a saturable transport system in the proximal small intestine. Riboflavin can be obtained directly from foods rich in the underivatized vitamin or after the hydrolysis of the coenzyme forms by nonspecific phosphatases and pyrophosphatases. The existence of riboflavin-binding immunoglobulins may represent a response of the immune system to stimulus by riboflavin or a flavin derivative.
