Structural and biochemical properties of fibroblast growth factor 23.

Fibroblast growth factor (FGF) 23 shares a fundamentally common structure with the members of the FGF family and has a unique sequence extension at the C-terminus. The molecular behavior of FGF23 as a systemic factor can be justified by the altered conformation of the beta-trefoil structure similar to that suspected in FGF19. On the other hand, the biological activity of FGF23 is quite distinct from those of other FGFs and requires the C-terminal unique extended structure. Two types of enzyme-linked immunosorbent assays (ELISA) have been developed to detect the intact mature form of FGF23 and its C-terminal portion. The former ELISA method enables the detection of rodent FGF23 and human FGF23. Studies on experimental animal models and laboratory examinations of physiologic and disordered conditions using these assays are contributing toward elucidating the physiology and pathophysiology of FGF23.