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. 2017 Feb 23;61(3):e02300-16. doi: 10.1128/AAC.02300-16

TABLE 2.

Kinetic parameters of the PER-7 and PER-8 enzymes in hydrolyzing β-lactams^a

β-Lactam	PER-7			PER-8
β-Lactam	K_m (μM)^b	k_cat (s⁻¹)^b	k_cat/K_m (μM⁻¹ s⁻¹)	K_m (μM)^b	k_cat (s⁻¹)^b	k_cat/K_m (μM⁻¹ s⁻¹)
Ampicillin	13 ± 4	52 ± 2	4.4	19 ± 3	54 ± 1	2.9
Penicillin G	13.7 ± 2.8	16.0 ± 0.2	1.2	13.7 ± 3.1	16.4 ± 0.3	1.2
Piperacillin	12.6 ± 3.6	0.60 ± 0.02	0.051	8.6 ± 1.8	0.65 ± 0.03	0.076
Cefepime	81 ± 7	10.2 ± 0.3	0.13	110 ± 16	12 ± 1	0.11
Cefmetazole	NH^c	NH	NH	NH	NH	NH
Cefotaxime	138 ± 63	84 ± 20	0.65	114 ± 17	70 ± 4	0.62
Cefoxitin	NH	NH	NH	NH	NH	NH
Ceftazidime	258 ± 22	33 ± 2	0.13	212 ± 26	31 ± 2	0.15
Cephradine	54 ± 5	62 ± 2	1.2	48 ± 8	66 ± 2	1.4
Moxalactam	NH	NH	NH	NH	NH	NH
Aztreonam	17 ± 3	8.8 ± 0.2	0.54	14 ± 2	8.8 ± 0.2	0.64
Imipenem	172 ± 33	0.13 ± 0.01	0.00076	101 ± 10	0.16 ± 0.01	0.0016
Meropenem	28 ± 8	0.13 ± 0.01	0.0051	32 ± 3	0.17 ± 0.01	0.0053

^a

The proteins were initially modified by the use of a His tag, which was removed after purification.

^b

K_m and k_cat values represent the means ± standard deviations of results of 3 independent experiments.

^c

NH, no hydrolysis was detected under conditions with substrate concentrations up to 1 mM and enzyme concentrations up to 700 nM.