Table I.

Comparison of observed cytochrome c oxidase (complex IV) turnover numbers during single and dual inhibition by CO, KCN, NO, CO + KCN, NO + KCN, NO + CO.

Inhibitor {concentration}	Turnover number (kcat, s-1)#
Uninhibited control*	346 ± 28
CO {0.5 mM}	190 ± 21
KCN {50 nM}	136 ± 8
NO {0.5 μM}	184 ± 30
CO {0.5 mM} & KCN {50 nM}	109 ± 9
KCN {50 nM} & NO {0.5 μM}	176 ± 8
NO {0.5 μM} & CO {0.5 mM}	182 ± 11

^*1.2 nM enzyme, pH 7.4 in 0.1 M sodium phosphate buffer, 1 mM EDTA, 0.05% lauryl maltoside, 22 °C.

^#Calculated from fits in Figure 1A, quoted errors are standard deviations.