. Author manuscript; available in PMC: 2011 Aug 10.

Published in final edited form as: Biochemistry. 2010 Aug 10;49(31):6737–6745. doi: 10.1021/bi100912m

Table 2.

Enzyme activity of wild type and R194H mutants of lf- and sfALR^a

Donor/Acceptor	k_cat (min⁻¹)	K_m (mM)	k_cat/K_m (M⁻¹ s⁻¹)
A) DTT / O₂
lfALR	61 ± 1.5	3 ± 0.3	330
lfALR R194H	72 ± 1	2.2 ± 0.1	550
sfALR	108 ± 7	1.6 ± 0.4	1100
sfALR R194H	73 ± 3	1.6 ± 0.25	760
B) Mia40^b / O₂
lfALR	42 ± 8	0.068 ± 0.021	10200
lfALR R194H	24 ± 4	0.042 ± 0.014	9600
C) Mia40^b / Cyt c
lfALR	48 ± 6	0.045 ± 0.012	17600
lfALR R194H	48 ± 9	0.039 ± 0.015	20700

Three assay systems were used: A) oxygen consumption in the oxygen electrode using DTT as a model substrate, B) the oxygen-dependent reoxidation of reduced Mia40 followed discontinuously with DTNB, and C) the reduction of cytochrome c followed continuously in the presence of reduced Mia40.

Kinetics determined with a shorter N-terminal linker for Mia40 than used previously (see Experimental Procedures (39)).