Fig. 8: Kinetic studies of the oxidation of thiocholine by 1 catalyzed by 2. [Se] = 2^.[2].

All experiments were conducted in 1 M Tris pH 7.5, at 25 ^oC, [Se] = 0.2 mM, [1] = 7.5 mM, [thiocholine] = 0.5–10 mM. Data were fitted by equation r = V_max^.S/(K_M + S): V_max = 3.73 ± 0.08^.10⁻⁵M s⁻¹, K_M = 7.8 ± 2.2·10⁻⁵M. This fitting is approximate because the rate of catalytic oxidation showed no significant drop even at 0.5 mM concentration of thiocholine, and lowering the concentration even more is experimentally challenging. Nevertheless, the data show clearly that K_M for thiocholine oxidation is significantly lower than for oxidation of 6. Error bars represent standard deviations based on three independent experiments.