How Supraphysiological Oxygen Levels in Standard Cell Culture Affect Oxygen-Consuming Reactions

Table 4

K_m(O₂) values for various O₂-consuming enzymes.

Enzyme	Product	Km(O2) (%)	Details	Reference
Nox2	O2^−	3.5		[77]
Nox2	O2^−	3.1		[78]
Nox2	O2^−	2-3		[19]
Nox2	O2^−	2-3		[79]
Nox4	H2O2	18		[78]
Nox4	H2O2	18		[19]
Nox4	H2O2	16–20		[79]
nNOS	NO	2.3	Purified bovine enzyme	[45]
nNOS	NO/O2^−	2.2	Partially uncoupled rat enzyme	[42, 43]
	O2^−	3.4	Fully uncoupled rat enzyme
nNOS	NO	15.7	Purified rat enzyme	[47]
nNOS	NO	39.8	Purified rat enzyme	[80]
nNOS	NO	28.5	Kinetic model based on rat enzyme data	[81, 82]
eNOS	NO	0.8	Purified bovine enzyme	[45]
eNOS	NO	0.3	Kinetic model based on rat enzyme data	[82, 83]
iNOS	NO	0.63 ± 0.09	Purified bovine enzyme	[45]
iNOS	NO	11.0	Isolated enzyme assay	[84]
iNOS	NO	10.6	Kinetic model	[82]
NOS	NO	3.1–10.8	Unspecified isoform	[48, 85]
XO	O2^·−/H2O2	2.2–6.8	Isolated from bovine milk	Fridovich et al. 1962, 1964
MAO	H2O2	3.4–28	Mammalian enzymes; various substrates	[86–88]; reviewed in [57]
HO	CO, iron, and bilirubin	<1.5	Unspecified isoform from chicken liver	[59]
LOX	H2O2	1–2.6	Unspecified isoform	[65]
COX-1	Various	0.4–3.1	Arachidonic acid substrate	[63, 89–91]
COX-2	Various	1.3–1.5	Arachidonic acid substrate	[63, 65]
PHD	Modified HIF	41–46	Various substrates	[92]
FIH	Modified HIF	4–12	Various substrates	[92]

Nox: NADPH oxidase; NOS: nitric oxide synthase; XO: xanthine oxidase; MAO: monoamine oxidase; HO: heme oxygenase; LOX: lipoxygenase; COX: cyclooxygenase; PHD: prolyl hydroxylase; FIH: factor inhibiting HIF-1.