How do the reported Kₘ(O₂) values for PHD2 (and FIH) quantitatively compare to the estimated ranges of intracellular O₂ concentration in relevant tissues (e.g., kidney, liver) under both normoxic and hypoxic conditions? A direct comparison in the text or a supplementary table would be invaluable.
Have there been studies or could the authors speculate on how factors such as subcellular localization (e.g., potential compartmentalization near mitochondria), local ascorbate/Fe²⁺/2OG availability, or protein-protein interactions (like PHD2-NACA) might modulate the effective Kₘ for O₂ or the local O₂ concentration experienced by the enzyme in cells? The in vitro kinetics may not capture these modulatory effects.
Given the potential for O₂ diffusion limitations and the enzyme’s slow reaction rate with O₂, what is the estimated turnover rate of PHD2 in vivo under steady-state normoxia? Is it sufficiently fast to account for the observed dynamics of HIF-α degradation upon re-oxygenation?How do the reported Kₘ(O₂) values for PHD2 (and FIH) quantitatively compare to the estimated ranges of intracellular O₂ concentration in relevant tissues (e.g., kidney, liver) under both normoxic and hypoxic conditions? A direct comparison in the text or a supplementary table would be invaluable.
Have there been studies or could the authors speculate on how factors such as subcellular localization (e.g., potential compartmentalization near mitochondria), local ascorbate/Fe²⁺/2OG availability, or protein-protein interactions (like PHD2-NACA) might modulate the effective Kₘ for O₂ or the local O₂ concentration experienced by the enzyme in cells? The in vitro kinetics may not capture these modulatory effects.
Given the potential for O₂ diffusion limitations and the enzyme’s slow reaction rate with O₂, what is the estimated turnover rate of PHD2 in vivo under steady-state normoxia? Is it sufficiently fast to account for the observed dynamics of HIF-α degradation upon re-oxygenation?
