The Roles of Fibroblast Growth Factor (FGF)-23, α-Klotho and Furin Protease in Calcium and Phosphate Homeostasis : A Mini-Review.

The roles of calcitonin, parathormone and calcitriol in the regulation of plasma calcium and phosphate are well-established. However, in autosomal-dominant hypophosphatemic rickety patients, studies have revealed normal plasma levels of calcium, associated with normal thyroid and parathyroid functions, but decreased levels of phosphate and calcitriol despite adequate reserves of vitamin D. Also, in tumoral calcinosis, persistent hyperphosphatemia with increased levels of 1,25(OH)2D3 have been observed.

Properties of the C-terminal domain of enzyme I of the Escherichia coli phosphotransferase system.

The bacterial phosphoenolpyruvate (PEP):glycose phosphotransferase system (PTS) mediates uptake/phosphorylation of sugars. The transport of all PTS sugars requires Enzyme I (EI) and a phosphocarrier histidine protein of the PTS (HPr). The PTS is stringently regulated, and a potential mechanism is the monomer/dimer transition of EI, because only the dimer accepts the phosphoryl group from PEP.

Transient state kinetics of Enzyme I of the phosphoenolpyruvate:glycose phosphotransferase system of Escherichia coli: equilibrium and second-order rate constants for the phosphotransfer reactions with phosphoenolpyruvate and HPr.

The first two reactions in the phosphotransfer sequence of bacterial phosphoenolpyruvate:glycose phosphotransferase systems are the autophosphorylation of Enzyme I by phosphoenolpyruvate followed by the transfer of the phospho group to the low-molecular weight protein, HPr. Transient state kinetic methods were used to estimate the second-order rate constants for both phosphotransfer reactions. These measurements support previous conclusions that only the dimer of Enzyme I, EI2, is autophosphorylated, and that the rate of formation of dimer is slow compared to the rate of its phosphorylation.