Table 2.

Kinetic parameters and metal content of mutants of URI from E. coli^a

Enzyme	kcat (s−1)	Km (mM)	kcat/Km (M−1 s−1)	URI/Zn
WT	196 ± 6	0.50 ± 0.05	(4.0 ± 0.4) × 105	0.90
H33N (H26)b	2.1 ± 0.1	(5.0 ± 0.4) × 10−2	(4.7 ± 0.4) × 104	0.07
H33A	0.60 ± 0.01	0.20 ± 0.01	(3.0 ± 0.2) × 103	0.20
H35N (H28)	4.0 ± 0.2	9.4 ± 1.1	(4.3 ± 0.5) × 102	<0.05
H35A	0.70 ± 0.04	39 ± 5	18 ± 2	<0.05
H59N (H49)	15 ± 1	0.70 ± 0.04	(2.1 ± 0.1) × 104	0.96
H59A	0.60 ± 0.01	0.70 ± 0.07	(8.3 ± 0.1 × 102	0.95
Y60F (Y50)	21.7 ± 0.1	0.16 ± 0.01	(1.4 ± 0.1) × 105	0.8
Y60A	13.9 ± 0.1	0.21 ± 0.01	(6.6 ± 0.3) × 104	0.8
R186K (R170)	54 ± 2	2.6 ± 0.2	(2.1 ± 0.2) × 104	0.94
R186M	4.7 ± 0.1	38 ± 3	(1.3 ± 0.1) × 102	0.91
D238N	60 ± 1	1.3 ± 0.1	(4.6 ±0.1) × 104	0.70
H297N (M258)	30 ± 2	56 ± 5	(5.0 ± 0.5) × 102	1.00
H297A	10 ± 1	(2.2 ± 0.3) × 102	43 ± 7	0.41
R302K (K303)	160 ± 4	2.5 ± 0.2	(6.3 ± 0.5) × 104	0.90
R302M	180 ± 9	(2.0 ± 0.3) × 102	(8.8 ± 1.3) × 102	0.99
W381F (W325)	16 ± 1	1.7 ± 0.1	(9.5 ± 0.4) × 103	0.90
W381A	250 ± 6	21± 2	(1.2 ± 0.1) × 104	0.69
D412N (D355)	0.60 ± 0.01	1.00 ± 0.04	(6.0 ± 0.3) × 102	0.36
D412A	(9.0 ± 0.3) × 10−3	0.40 ± 0.05	21 ± 3	0.12
R414K (R357)	5.8 ± 0.1	0.82 ± 0.02	(7.1 ± 0.2) × 103	0.92
R414M	0.70 ± 0.01	1.4 ± 0.1	(5.4 ± 0.2) × 102	0.91

^aThese data were obtained at 30 °C, pH 8.0, with D-glucuronate as the substrate.

^bThe corresponding residue numbers for Bh0493.