Table 2.

Steady-state kinetic parameters and sKIE^a

Substrate	Solvent		wt	D143A	D143H	R232A
ABTS (H2O2)	H2O	kcat (s−1)	(3.54 ± 0.01) × 103 [(3.73 ± 0.02) × 103]	(3.45 ± 0.02) × 10 [(4.62 ± 0.01) × 10]	(4.37 ± 0.05) × 102 [(4.16 ± 0.08 × 102]	(4.87 ± 0.06) × 102 [(5.25 ± 0.02) × 102]
		KM (μM)	(6.07 ± 0.01) × 102 [(2.02 ± 0.04) × 103	(4.80 ± 0.20) × 102 [(7.50 ± 0.20) × 104]	(2.50 ± 0.05) × 103 [(4.90 ± 0.30) × 103]	(1.30 ± 0.02) × 103 [(1.35 ± 0.02) × 104]
		kcat/KM (s−1·M−1)	(5.80 ± 0.10) × 106 [(1.85 ± 0.03) × 106]	(7.20 ± 0.30) × 104 [(6.10 ± 0.10) × 102]	(1.75 ± 0.02) × 105 [(8.40 ± 0.40) × 104]	(3.76 ± 0.03) × 105 [(3.90 ± 0.10) × 104]
	D2O	kcat (s−1)	(5.10 ± 0.20) × 103		(3.92 ± 0.08) × 102
		KM (μM)	(1.00 ± 0.10) × 102		(2.95 ± 0.05) × 102
		kcat/KM (s−1·M−1)	(5.10 ± 0.20) × 107		(1.33 ± 0.05) × 106
	sKIE	D(kcat)	0.69 ± 0.02		1.11 ± 0.04
		D(kcat/KM)	0.11 ± 0.01		0.13 ± 0.01
RB19 (H2O2)	H2O	kcat (s−1)	(1.67 ± 0.08) × 102 [(1.69 ± 0.01) × 102]	(2.92 ± 0.03) × 100 [(3.80 ± 0.20) × 100]	(1.22 ± 0.02) × 10 [(1.77 ± 0.04) × 10]	(2.30 ± 0.05) × 10 [(3.10 ± 0.10) × 10]
		KM (μM)	(3.90 ± 0.30) × 10 [(3.70 ± 0.10) × 102]	(3.93 ± 0.05) × 10 [(1.60 ± 0.20) × 104]	(7.70 ± 0.20) × 10 [(5.70 ± 0.40) × 102]	(4.60 ± 0.20) × 10 [(2.20 ± 0.20) × 103]
		kcat/KM (s−1·M−1)	(4.20 ± 0.10) × 106 [(4.60 ± 0.10) × 105]	(7.40 ± 0.10) × 104 [(2.40 ± 0.20) × 102]	(1.60 ± 0.30) × 105 [(3.10 ± 0.40) × 104]	(5.00 ± 0.30) × 105 [(1.40 ± 0.20) × 104]

^aValues shown in square brackets are parameters for H₂O₂.