. Author manuscript; available in PMC: 2010 Jul 1.

Published in final edited form as: Arch Biochem Biophys. 2009 May 22;487(1):10–18. doi: 10.1016/j.abb.2009.05.008

Table 3.

Rates of Rieske center reduction and oxidation in PDO WT and the mutants.

	Rieske center Reduction by PDR^*				Rieske center Oxidation^***
	k_re₁, s⁻¹	A_re1, %	k_re₂, s⁻¹	A_re2, %	k_ox₁, s⁻¹	A_ox1, %	k_ox₂, s⁻¹	A_ox1, %
WT	94	64	2.0	36	49	60	0.23	9
K117A	31	81	0.7	19	57	54	0.23	9
K119A	90	65	1.1	35	53	41	0.16	10
H120A	72	69	2.2	31	59	68	0.35	9
K121A	80	61	1.8	39	49	79	0.17	10
Y123A	50	69	2.9	31	49	60	0.18	5
5 point variant	16	74	1.6	26	59	63	0.08	5
W94Y	22	100	n.d. ^**	n.d.	35	52	n.d. ^**	n.d.
W94F	25	100	n.d. ^**	n.d.	32	40	n.d. ^**	n.d.
W94A	74	72	1.4	28	19	31	0.11	11

Anaerobicallyreduced PDR (15 μM) was mixed with anaerobic oxidized PDO (15f μM) (concentration before mixing). Enzymes were in 0.1M HEPES, pH 7.8, containing 3 mM phthalate. A_re1 and A_re2 denote the fractions of the Rieske centers reduced based on the two fastest observed phases of semiquinone formation in PDR. In all samples the fast phase (k_re₁) accounted for reduction of only 35–40% of all available Rieske centers.

^**

n.d. – phase was not detected. An increased contribution of a slower, 1–4 10⁻² s⁻¹ reduction phase (for Rieske center reduction by PDR) or 1–4 10⁻³ s⁻¹ oxidation phase (for Rieske center oxidation) was observed but not evaluated in this study, because such phases are not physiologically significant.

^***

Anaerobically reduced PDO (20 μM) in 0.1M HEPES, pH 7.8 in the presence of 3 mM phthalate was mixed with the same buffer containing 3 mM phthalate and 250 μM O₂ (concentration before mixing). A_ox1 and A_ox2 denote the fraction of the Rieske centers oxidized during the respective oxidation phase. Total contribution of these two fast phases account to less than 100% of all available Rieske centers due to the contributing of slower (> 5 10⁻³ s⁻¹) oxidation phases.