. 2024 Oct 1;56(10):2260–2270. doi: 10.1038/s12276-024-01323-x

Table 1.

Ferryl reduction by ascorbate.

	α subunit				γ subunit
	V_max (s⁻¹)	K_m (µM)	Linear (M⁻¹ s⁻¹)	V_max/K_m (μM⁻¹ s⁻¹)×10⁻³	V_max (s⁻¹)	K_m (µM)	Linear (M⁻¹ s⁻¹)	V_max/K_m (μM⁻¹ s⁻¹)×10⁻³
F1	0.0244 ± 0.0019	15.7 ± 3.53	41.9 ± 3.6	1.55 ± 0.37	0.0056 ± 0.0056	227.8 ± 300.3	8.99 ± 4.70	0.025 ± 0.041
F3	0.0250 ± 0.0018	2.71 ± 1.11	11.0 ± 3.4	9.22 ± 3.84	0.0102 ± 0.0021	13.2 ± 9.38	1.93 ± 3.20	0.77 ± 0.57
F5	0.0259 ± 0.0021	17.4 ± 4.55	14.9 ± 3.1	1.49 ± 0.41	0.0022 ± 0.00043	46.0 ± 21.6	6.13 ± 0.52	0.048 ± 0.024
F6	0.0270 ± 0.0026	15.2 ± 4.57	21.6 ± 5.1	1.78 ± 0.56	0.0037 ± 0.00074	40.0 ± 19.9	8.80 ± 0.92	0.093 ± 0.05
F7	0.0234 ± 0.0017	11.7 ± 3.03	23.2 ± 2.8	2.00 ± 0.54	Not measurable	Not measurable	10.5 ± 0.95	Not measurable
F9	0.0308 ± 0.0023	5.35 ± 2.03	10.1 ± 4.0	5.76 ± 2.23	0.0097 ± 0.0015	4.6 ± 3.80	12.8 ± 2.7	2.11 ± 1.77
F10	0.0280 ± 0.0027	5.12 ± 2.13	29.3 ± 4.4	5.47 ± 2.34	0.0120 ± 0.0026	37.1 ± 18.9	7.52 ± 3.18	0.32 ± 0.18

The rate constants of ferryl reduction by the α and γ subunits were fitted to a rectangular hyperbola plus a straight line, offsetting the measured autoreduction rates to obtain the V_max and K_m plus a linear rate constant. Notably, the high fit values and errors indicate that this approach is unsuitable for the γ subunit in the absence of a tyrosine insert (F1 and F7; in the latter case, the errors are an order of magnitude larger than the values and are not recorded in the table). Errors in V_max and K_m are SEMs of the nonlinear curve fit. The SEM of the ratio V_max/K_m was approximated from the respective SEM, assuming that the variables were independent and using a first-order Taylor expansion. Var(x/y) =x²/y² × (Var(x)/x² + Var(y)/y²).