Recombinant human FGF-23 protein

FGF-23, also known as fibroblast growth factor 23, is a member of the FGF family which is responsible for phosphate and vitamin D metabolism. The main function of this protein seems to be regulation of phosphate concentration in plasma. It is secreted by osteocytes in response to elevated calcitriol and acts on the kidneys, where it decreases the expression of NPT2, a sodium-phosphate cotransporter in the proximal tubule. Thus, FGF-23 interaction with renal proximal tubular epithelium decreases the reabsorption and increases excretion of phosphate. This protein may also suppress 1-alpha-hydroxylase, reducing its ability to activate vitamin D and subsequently impairing calcium absorption. Following secretion this protein is inactivated by cleavage into a N-terminal fragment and a C-terminal fragment. The N-terminal sequence analysis is showing that a C-terminal fragment is detected. Recombinant human FGF-23, fused to His-tag at C-terminus, was expressed in insect cell and purified by using conventional chromatography techniques.