. Author manuscript; available in PMC: 2010 Nov 17.

Published in final edited form as: Biochemistry. 2009 Nov 17;48(45):10716–10723. doi: 10.1021/bi901205w

Table 1.

Kinetic parameters for steady state turnover of AA-inhibited cyt bc₁ complex. f_SOP is the fraction of Q-cycle bypass reactions resulting in superoxide production derived from the superoxide dismutase sensitivity of cyt c reduction in the AA-inhibited complex. Product inhibition constants K_i for a mixed inhibition model are for uninhibited steady –state turnover driven by decyl-ubiquinol. K_m and K_i are reported in units of μM. Rates of quinol oxidation are given in s⁻¹ from total bypass reactions (V_max(bypass)) and from superoxide-producing bypass reaction (V_max(SO)). In two cases, V_max(SO) could not be measured but is estimated as a range: 0.5–0.75 V_max(bypass) covering the range of measured f_SOP. Rates noted in italics were measured by stopped flow. The shift in redox potential for the Q/QH₂ couple based on measured values of K_m and the competitive K_i are reported in V.

Substrate	K_m	V_max(bypass)	f_SOP	V_max(SO)	K_i(C)	K_i (NC)	ΔE_m
(1)	23	2.4	0.68	1.6	2.1	-	−0.060
(2)	25	2.2	-	1.1–1.7	11.8	5.8	−0.019
(3)	5	0.6	0.66	0.4	-	-	-
(4)	>150	7.5	0.71	5.3	-	-	-
(5)	9	27	0.55	15.1	4.4	7.1	−0.018
(6)	35	80	-	40–60	-	-	-
(7)	30	199	0.51	101	26.2	36.8	−0.003