Table 2.

Kinetic parameters of human GST A1-1 and its mutated variants compared to those of human GST A4-4

Enzyme	CDNB			Hexenal			Nonenal
	Km, mM	kcat, s−1	kcat/Km, mM−1⋅s−1	Km, mM	kcat, s−1	kcat/Km, mM−1⋅s−1	Km, mM	kcat, s−1	kcat/Km, mM−1⋅s−1
A1-1	0.56  ± 0.04*	88  ± 3*	160*	0.18  ± 0.02	0.22  ± 0.02	1.2  ± 0.1	0.025  ± 0.004	0.13  ± 0.01	5.0  ± 0.6
mut1	3.2  ± 1.9	62  ± 25	19  ± 4	ND	ND	0.059  ± 0.008	0.051  ± 0.012	0.70  ± 0.09	14  ± 2
mut2	4.2  ± 1.3	99  ± 22	24  ± 2	0.90  ± 0.36	2.5  ± 0.9	2.7  ± 0.1	0.035  ± 0.004	0.79  ± 0.03	23  ± 2
mut3	3.7  ± 1.7	29  ± 9	7.9  ± 1.1	ND	ND	4.7  ± 0.2	0.035  ± 0.008	0.60  ± 0.05	17  ± 3
Ghelix	12  ± 9	81  ± 55	7.0  ± 0.7	0.48  ± 0.10	3.2  ± 0.7	6.8  ± 0.2	0.076  ± 0.012	4.3  ± 0.4	57  ± 5
GIMFhelix	3.4  ± 2.2	48  ± 22	14  ± 3	0.43  ± 0.09	48  ± 9	113  ± 4	0.014  ± 0.002	21  ± 1	1,520  ± 120
A4-4	5.8  ± 1.4†	46  ± 9†	7.9†	0.36  ± 0.23	13  ± 7	37  ± 4	0.180  ± 0.050	89  ± 18	485  ± 43

Substrate-saturation curves were measured by using CDNB (0.2–1.8 mM) or alkenals (0.01–0.10 mM) as the varied substrate at constant concentration of glutathione (5 mM and 0.5 mM, respectively). Higher substrate concentrations could not be used for reasons of limited solubility and high absorbance. However, k_cat/K_m values could still be determined with adequate precision by fitting v = (k_cat/K_m) [S] [E]_o/(1 + [S]/K_m) to the experimental data. ND, not possible to determine. 

^*From ref. 30. 

^†From ref. 13.