. Author manuscript; available in PMC: 2015 Aug 8.

Published in final edited form as: Biochemistry. 2010 Mar 16;49(10):2150–2158. doi: 10.1021/bi9021507

Table 1.

CO, O₂, and NO Binding to Ferrous Heme Complexes^a

	CO (Fe^II)			O₂ (Fe^II)				NO (Fe^II)

	k _on	k _off	K _D	k _on	k _off	K _D	M	k _on	k _off	K _D	E _m7	ref
chelated protoheme	11000	25 × 10⁻³	2.3 × 10⁻³	62000	4200	68	29500	180	2.9 × 10⁻⁴	1.6 × 10⁻⁶	−80	83 – 85
MPO	0.14	226 × 10⁻³	1650	11	1.92	173	0.10	100	4.6	46	5	25, 2828
EPO	0.65	12 × 10⁻³	19	37	nd	nd		1300	24	19	nd	28
LPO	0.59	1.3 × 10⁻³	2.2	38	11.2	295	134	140	0.25	1.8	−191	28, 86, 87
	1.4	29 × 10⁻³	21
HRP	3	0.1 × 10⁻³	33 × 10⁻³	53	0.1	1.9	58	nd	nd	nd	−278	62, 88, 89
CcP	2	9.2 × 10⁻³	4.6	45				0.22	nd	nd	−194	90 – 92
Mb	990	36 × 10⁻³	37 × 10⁻³	16000	15.6	0.98	26	17000	1.2 × 10⁻⁴	7 × 10⁻⁶	46	92 – 95
trHbO	14	4 × 10⁻³	0.29	110	1.4 × 10⁻³	13 × 10⁻³	0.05	180	nd	nd	nd	73
alHbO	190	18 × 10⁻³	95 × 10⁻³	1500	4 × 10⁻³	2.7 × 10⁻³	0.03	5600	nd	nd	nd	74
CcO	70	23 × 10⁻³	0.30	100000	45000	450	1500	100000	0.13	0.013	350	95 – 97
chloroperoxidase	72	2.2	31	550	12	22	0.71	nd	nd	nd	−140	92, 98, 99
cytochrome P450_cam	37	0.14	3.8	770	1.1	1.4	0.37				−170	98 – 100

Data cited are the association (k_on, ×10³ M⁻¹ s⁻¹) and dissociation (k_off, s⁻¹) rate constants, the corresponding dissociation constant (K_D, μM), the partition coefficient (M) for discrimination of CO versus O₂ (from ratio of K_D values), and the Fe^III/Fe^II midpoint potential measured at pH 7.0 (E_m7, mV); nd, not determined.