TABLE 1.

β-Lactam hydrolysis by TEM-1, AmpC, and CTX-M enzymes

Substrate	Parameter	Value for enzyme:
		TEM-1	AmpC	CTX-M-14	CTX-M-15	CTX-M-15 P167S
Nitrocefin	kcat (s−1)	710 ± 80	940 ± 180	370 ± 27	210 ± 8	77 ± 3
	Km (μM)	30 ± 10	760 ± 100	21 ± 3	6.3 ± 0.9	7.6 ± 1.2
	kcat/Km (μM−1 s−1)	24 ± 8.4	0.8 ± 0.19	18 ± 2.9	33 ± 4.9	10 ± 1.6
Ceftazidime	kcat (s−1)	NDa	0.11 ± 0.0094	ND	ND	3.09 ± 0.61
	Km (μM)	>1,000	45 ± 13	ND	ND	600 ± 170
	kcat/Km (μM−1 s−1)	0.0002	0.0025 ± 0.00075	0.0011 ± 0.000070	0.014 ± 0.0010	0.0051 ± 0.0018
Ceftibuten	kcat (s−1)	HNDb	0.15 ± 0.011	26 ± 3	34 ± 1	33 ± 2
	Km (μM)	HND	1.8 ± 0.77	250 ± 49	98 ± 11	190 ± 23
	kcat/Km (μM−1 s−1)	HND	0.085 ± 0.037	0.10 ± 0.023	0.35 ± 0.041	0.17 ± 0.023
Imipenem	kcat (s−1)	0.02 ± 0.0011	0.058 ± 0.0026	0.0048 ± 0.00039	0.0046 ± 0.00027	0.0022
	Km (μM)	16 ± 2.8	30 ± 3	2.2 ± 0.92	3.1 ± 0.75	<2.5
	kcat/Km (μM−1 s−1)	0.0013 ± 0.00024	0.0019 ± 0.00021	0.0022 ± 0.00094	0.0016 ± 0.00040	>0.009
Meropenem	kcat (s−1)	0.00053 ± 0.000022	0.013 ± 0.0019	0.003 ± 0.00020	0.0072 ± 0.00052	0.0045 ± 0.0017
	Km (μM)	<5	83 ± 22	4.2 ± 1.1	2.2 ± 0.16	3.6 ± 2.0
	kcat/Km (μM−1 s−1)	>0.00011	0.00016 ± 0.000048	0.00072 ± 0.00020	0.0032 ± 0.00033	0.0013 ± 0.00087
Ertapenem	kcat (s−1)	0.0010 ± 0.000036	0.012 ± 0.0004	0.0024 ± 0.00044	0.0038	0.0058 ± 0.00074
	Km (μM)	<5	4.6 ± 0.54	8.5 ± 4.7	<5	4.5 ± 2.0
	kcat/Km (μM−1 s−1)	>0.00021	0.0026 ± 0.00032	0.00028 ± 0.00016	>0.00076	0.0013 ± 0.00060
Tebipenem	kcat (s−1)	0.00072 ± 0.000034	0.0022 ± 0.00028	0.0031 ± 0.00032	0.008	0.0036 ± 0.00052
	Km (μM)	5.1 ± 1.2	7.2 ± 2.7	11 ± 2.8	<5	6.1 ± 2.7
	kcat/Km (μM−1 s−1)	0.00014 ± 0.000034	0.00031 ± 0.00012	0.00028 ± 0.000077	>0.0016	0.00059 ± 0.00028

^aND, not determined.

^bHND, hydrolysis not detected.