Kinetic Investigations of the Role of Factor Inhibiting Hypoxia-inducible Factor (FIH) as an Oxygen Sensor.

摘要: The hypoxia-inducible factor (HIF) hydroxylases regulate hypoxia sensing in animals. In humans, they comprise three prolyl (PHD1–3 or EGLN1–3) and inhibiting HIF (FIH). FIH is an asparaginyl hydroxylase catalyzing post-translational modification of HIF-α, resulting reduction HIF-mediated transcription. Like the PHDs, proposed to have a hypoxia-sensing role cells, enabling responses changes cellular O2 availability. PHD2, most important human PHD isoform, be biochemically/kinetically suited as sensor due its relatively high sensitivity concentration slow reaction with O2. To ascertain whether these parameters are conserved among hydroxylases, we compared reactions PHD2 Consistent previous reports, found lower Kmapp(O2) values for than all HIF-derived substrates. Under pre-steady-state conditions, O2-initiated significantly faster that PHD2. We then investigated kinetics respect ankyrin repeat domain (ARD) has tested ARDs HIF-α substrates, were results correlate studies showing active at concentrations PHDs suggest competition between likely biologically relevant, particularly hypoxic conditions. overall consistent proposal kinetic properties individual oxygenases reflect their biological capacity act sensors.