Table 4. Reported Km values of O2-dependent enzymes.
Km values vary based on the assay method and tested substrate. Some enzymes have multiple Km values listed, reflecting measurements from different studies.
| Category | Enzyme* | Km for O2 | Assay details | Reference |
|---|---|---|---|---|
| Dioxygenase | PHD2 (EGLN1) | 250 μM | In vitro radioactivity 2-OG turnover assay with HIF1α (556–574) peptide as substrate | Hirsilä et al., 2003 |
| 1746 μM | In vitro time-resolved fluorescence resonance energy transfer assay with P564-HIF1α peptide (DLEMLAPYIPMDDDFQL) as substrate | Dao et al., 2009 | ||
| 67 μM | In vitro O2 consumption assay with HIF1α (502–697) peptide as substrate | Ehrismann et al., 2007 | ||
| 81 μM | In vitro O2 consumption assay with HIF1α (530–698) peptide as substrate | Ehrismann et al., 2007 | ||
| PHD1 (EGLN2) | 230 μM | In vitro radioactivity 2-OG turnover assay with HIF1α (556–574) peptide as substrate | Hirsilä et al., 2003 | |
| PHD3 | 230 μM | In vitro radioactivity 2-OG turnover assay with HIF1α (556–574) peptide as substrate | Hirsilä et al., 2003 | |
| KDM4E | 197 μM | In vitro O2 consumption assay with ARK(me3)STGGK peptide as substrate | Cascella and Mirica, 2012 | |
| KDM4A | 173 μM | In vitro MALDI-TOF-MS assay with H31−15K9me3 peptide as substrate | Hancock et al., 2017 | |
| 57 μM | In vitro O2 consumption assay with ARK(me3)STGGK peptide substrate | Cascella and Mirica, 2012 | ||
| 60 μM | In vitro radioactivity 2-OG turnover assay with histone H3(1–19)K9me3 as substrate | Chakraborty et al., 2019 | ||
| KDM6A | 180 μM | In vitro radioactivity 2-OG turnover assay with histone H3(21–44)K27(me3) as substrate | Chakraborty et al., 2019 | |
| KDM4C | 158 μM | In vitro O2 consumption assay with ARK(me3)STGGK peptide substrate | Cascella and Mirica, 2012 | |
| KDM4B | 150 μM | In vitro radioactivity 2-OG turnover assay with histone H3(1–19)K9me3 as substrate | Chakraborty et al., 2019 | |
| FIH | 90 μM | In vitro radioactivity 2-OG turnover assay with HIF1α (788–822) peptide as substrate | Koivunen et al., 2004 | |
| KDM5A | 90 μM | In vitro radioactivity 2-OG turnover assay with histone H3(1–21)K4me3 as substrate | Chakraborty et al., 2019 | |
| KDM3A | 75 μM (7.6% O2) † | In vitro demethylation-formaldehyde dehydrogenase-coupled reaction assay with K224-monomethylated PGC-1α peptide as substrate | Qian et al., 2019 | |
| KDM5B | 40 μM | In vitro radioactivity 2-OG turnover assay with histone H3(1–21)K4me3 as substrate | Chakraborty et al., 2019 | |
| P4HA1 | 40 μM | Standard P4H activity assay with (Pro-Pro-Gly)10 (Peptide Institute) as a substrate | Hirsilä et al., 2003 | |
| KDM5C | 35 μM | In vitro radioactivity 2-OG turnover assay with histone H3(1–21)K4me3 as substrate | Chakraborty et al., 2019 | |
| TET1 | 30 μM | In vitro radioactivity 2-OG turnover assay with oligonucleotides containing a 5-mC as substrate | Laukka et al., 2016 | |
| 3.0 μM (0.31% O2) † | In vitro DNA hydroxymethylation assay with genomic DNA as substrate | Thienpont et al., 2016 | ||
| TET2 | 30 μM | In vitro radioactivity 2-OG turnover assay with oligonucleotides containing a 5-mC as substrate | Laukka et al., 2016 | |
| 5.2 μM (0.53% O2) * | In vitro DNA hydroxymethylation assay with genomic DNA as substrate | Thienpont et al., 2016 | ||
| KDM5D | 25 μM | In vitro radioactivity 2-OG turnover assay with histone H3(1–21)K4me3 as substrate | Chakraborty et al., 2019 | |
| KDM6B | 20 μM | In vitro radioactivity 2-OG turnover assay with histone H3(21–44)K27(me3) as substrate | Chakraborty et al., 2019 | |
| IDO1 | 11.5–24 μM | In vitro O2 consumption assay with L-Trp as substrate | Kolawole et al., 2015 | |
| PTGS1 | 10 μM (sheep) | In vitro radioactivity label assay with [1-14C]arachidonic acid as substrate | Juránek et al., 1999 | |
| PTGS2 | 13 μM (mouse) | In vitro radioactivity label assay with [1-14C]arachidonic acid as substrate | Juránek et al., 1999 | |
| ALOX5 | 13 μM (porcine) | In vitro radioactivity label assay with [1-14C]arachidonic acid as substrate | Juránek et al., 1999 | |
| ALOX12 | 13 μM | In vitro radioactivity label assay with [1-14C]arachidonic acid as substrate | Juránek et al., 1999 | |
| ALOX15 | 26 μM (porcrine) | In vitro radioactivity label assay with [1-14C]arachidonic acid as substrate | Juránek et al., 1999 | |
| ALOX15 | 26 μM (rabbit) | In vitro radioactivity label assay with [1-14C]arachidonic acid as substrate | Juránek et al., 1999 | |
| ADO | >500 μM | In vitro UPLC-MS-TOF assay with RGS4(2–15) peptide as substrate | Masson et al., 2019 | |
| Monooxygenase |
NOS1
(nNOS) |
350 μM (rat) | In vitro heme-NO complex formation assay with L-arginine as substrate | Abu-Soud et al., 1996 |
|
NOS2
(iNOS) |
130 μM (mouse) | In vitro heme-NO complex formation assay with L-arginine as substrate | Abu-Soud et al., 2001 | |
| NOS3 (eNOS) |
4 μM (bovine) | In vitro heme-NO complex formation assay with L-arginine as substrate | Abu-Soud et al., 2000 | |
| 25 μM (bovine) | In vitro heme-NO complex formation assay with N-hydroxy-L-arginine as substrate | Abu-Soud et al., 2000 | ||
| TH | 16.2 μM (low-activity state); 46.1 μM (high- activity state); |
In vitro radioactivity label assay with 3H-tyrosine as substrate | Rostrup et al., 2008 | |
| 12.6–26.7 μM (low-activity state); 28.8–42.9 μM (high-activity state)‡; |
In vitro oxygraphic assay with tyrosine as substrate | Rostrup et al., 2008 | ||
| 2.6–3.9 μM (2–3 mmHg, rat) * | In vitro radioactivity label assay with 3H-tyrosine as substrate | Katz, 1980 | ||
| TPH1 | 3.9~12.9 μM (3–10 mmHg, rat) † | In vitro radioactivity label assay with 3H-tryptophan as substrate | Katz, 1980 | |
| PAH | 17 μM | In vitro oxygraphic assay with phenylalanine as substrate | Rostrup et al., 2008 | |
| PAM | 70 μM (rat) | In vitro radioactivity label assay with [α-2H2]-N-acylglycine of different chain length as substrates | McIntyre et al., 2010 | |
| Oxidase | Cytochrome c oxidase | <0.1 μM (rat) | In vitro O2 consumption assay measuring O2 consumption of purified rat mitochondria at low phosphate potential ([ATP]/[ADP]*[Pi]) | Bienfait et al., 1975 |
| 1–3 μM (rat) | In vitro O2 consumption assay measuring O2 consumption of purified rat mitochondria at high phosphate potential | Bienfait et al., 1975 | ||
| 0.5 μM (mouse) | Cellular assay measuring the ‘apparent K (m)’ for O2 or p 50 of respiration in 32D cells using high-resolution respirometry | Scandurra and Gnaiger, 2010 | ||
| AOC3 | 38 μM | In vitro enzymatic assay using purified human AOC3 | Shen et al., 2012 |
*
O2-dependent enzymes that are known sensors are highlighted in bold; that are reported to be inhibited under hypoxia are highlighted in a light orange background; that are reported to be associated with positive selections in high-altitude populations are highlighted in red (also see Table 6).
†
Km of these enzyme were reported with units as % O2 or mmHg, and calculated according to Mas-Bargues et al., 2019; Place et al., 2017.
‡
Combined data for TH1/3/4 splicing isoforms.