TABLE 1.

Steady-state enzyme kinetics of TMB-1, TMB-2, and TMB-1 mutants

Compounda	TMB-1			TMB-2			TMB-1 E119Q			TMB-1 E119S			TMB-1 E119A
	Km (μM)	kcat (s−1)	kcat/Km (s−1/μM)	Km (μM)	kcat (s−1)	kcat/Km (s−1/μM)	Km (μM)	kcat (s−1)	kcat/Km (s−1/μM)	Km (μM)	kcat (s−1)	kcat/Km (s−1/μM)	Km (μM)	kcat (s−1)	kcat/Km (s−1/μM)
Penicillins
Benzylpenicillin	88 ± 20	78 ± 4	0.9	93 ± 19	67 ± 4	0.7	242 ± 35	33 ± 2	0.1	228 ± 40	59 ± 5	0.3	176 ± 50	146 ± 12	0.8
Ampicillin	71 ± 13	95 ± 4	1.3	263 ± 26	68 ± 2	0.3	103 ± 20	58 ± 3	0.6	102 ± 15	83 ± 3	0.8	84 ± 18	57 ± 3	0.7
Piperacillin	69 ± 14	57 ± 5	0.8	56 ± 10	34 ± 2	0.6	147 ± 29	29 ± 3	0.2	150 ± 30	69 ± 7	0.5	149 ± 23	53 ± 4	0.4
Cephalosporins
Cefotaxime	26 ± 3	19.8 ± 0.6	0.8	15.5 ± 1.6	10.2 ± 0.3	0.7	8.9 ± 0.7	5.2 ± 0.1	0.6	15 ± 2	9.9 ± 0.3	0.7	14 ± 1	15.0 ± 0.3	1.04
Ceftazidime (R2,+)	22.4 ± 3.4	4.0 ± 0.2	0.18	17.3 ± 1.7	1.9 ± 0.05	0.1	13 ± 1	2.7 ± 0.08	0.2	13 ± 2	4.8 ± 0.2	0.37	17 ± 1	5.6 ± 0.1	0.3
Cefepime (R2,+)	194 ± 22	13.2 ± 0.6	0.07	170 ± 12	7.1 ± 0.3	0.04	124 ± 7	6.3 ± 0.2	0.05	139 ± 11	16.2 ± 0.7	0.1	234 ± 17	19.3 ± 0.8	0.08
Cefoxitin	12 ± 2	8.2 ± 0.3	0.7	10 ± 1	4.7 ± 0.05	0.47	2.9 ± 0.5	1.06 ± 0.02	0.9	3.9 ± 0.6	2.2 ± 0.04	0.6	5.07 ± 0.95	2.9 ± 0.08	0.9
Carbapenems
Meropenem	36 ± 3	23.8 ± 0.4	0.7	27 ± 3	13.2 ± 0.4	0.5	19 ± 2	10.3 ± 0.2	0.5	34 ± 3	27.2 ± 0.5	0.8	29 ± 3	19.1 ± 0.5	0.7
Imipenem (R2,+)	126 ± 6	43.1 ± 0.6	0.3	108 ± 6	23.4 ± 0.4	0.2	98 ± 4	14.3 ± 0.1	0.1	96 ± 7	27.6 ± 0.6	0.3	131 ± 11	30.5 ± 0.8	0.2
Doripenem	97 ± 10	671 ± 20	7	85 ± 4	385 ± 5	4.6	58 ± 3	211 ± 3	3.7	65 ± 4	413 ± 7	6.4	63 ± 3	491 ± 6	7.8

^a“(R2,+)” indicates that the substrate contained a positively charged R2 group.