Table 1.

Parameters for the degradation of HIF1α in normoxia

Constant Value Temperature (°C) Reference
[H2O2]0 0.20 μM* 37 Gonzalez-Flecha and Demple, 1997
[O2]0 200 μM 37 Tuckerman et al., 2004
[Fe3+]0 0 μM 37 -
[Fe2+]0 50 μM 37 Tuckerman et al., 2004
[2-OG]0 1000 μM 37 Tuckerman et al., 2004
[Asc]0 1000 μM 37 Tuckerman et al., 2004
[HIF1α]0 1 μM 37 Tuckerman et al., 2004
[PHD2]0 1 μM; 4 nm (where stated for in vitro comparisons) 37 Tuckerman et al., 2004
kon,Fe2 18 μM-1 min-1, estimate 37 -
koff,Fe2 36 min-1, estimate 37 -
kcat,Fe2 0, assumed 37 -
Km,Fe2 2 μM (0.03 μM) 37 Hirsila et al., 2005; Koivunen et al., 2004
kon,DG 1.8×10-1 μM-1 min-1, estimate 37 -
koff,DG 10.8 min-1 estimate 37 -
kcat,DG 0, assumed 37 -
Km,DG 60 μM 37 Hirsila et al., 2003
kon,O2 4.3×10-2 μM-1 min-1, estimate 37 -
koff,O2 10.8 min-1, estimate 37 -
kcat,O2 0, assumed 37 -
Km,O2 250 μM 37 Hirsila et al., 2003
kon,AS 1.8×10-2 μM-1 min-1, estimate 37 -
koff,AS 3.6 min-1, estimate 37 -
kcat,AS 0, assumed 37 -
Km,AS 180 μM 37 Hirsila et al., 2003
kon,Hα 1.1×10-1 μM-1 min-1, estimate calculated 37 -
koff,Hα 0.7 min-1, estimate 37 -
kcat,Hα 0.098-0.164 min-1, estimate 0.08-10 min-1 min/max from experiments 37; 30 Kersteen et al., 2004; Tuckerman et al., 2004
Km,Hα 7 μM 37 Hirsila et al., 2003
kFe3 1.1×10-2 μM-1 min-1, 1.6×10-2 μM-1 min-1 30 Beltran et al., 1998; Lovstad, 2003; Millero and Sotolongo, 1989
kASFe 6×10-3 μM-1 min-1 37 Buettner and Jurkiewicz, 1996
kon,VL 42 μM-1 min-1 25 Hon et al., 2002
koff,VL 1.3 min-1 25 Hon et al., 2002
  • Values are experimentally determined or estimated, or estimated from model calculations as noted

  • * Assumed, as an approximation. Range of 0.13-0.25 μM given in the cited reference. Within this range, the effects on varying H2O2 initial concentration on the model response are relatively negligible

  • Maximum is estimated from Kersteen et al. (Kersteen et al., 2004), where kcatHα=13±1 min-1 for (Pro-Pro-Gly) binding to PHD2; 9.2±1.2 min-1 for dansyl-GFPG-OE to PHD2. The model default value, 1 min-1, is closer to the minimum, estimated from Tuckerman et al. (Tuckerman et al., 2004)

  • For the Fenton reaction at pH 3-4, kFe3 is 76.52 M-1 s-1 (Beltran et al., 1998); this value is approximately threefold higher at pH 8 (Millero and Sotolongo, 1989). For pH 6.7 (the pH assumed for all other model kinetic parameters), kFe3 was estimated from Beltran et al. (Beltran et al., 1998) as 6.7/8*3*76.52 M-1 s-1=1.1×10-2 μM-1 min-1, which corresponds with that reported by Lovstad (Lovstad, 2003)