TABLE 2.

Kinetic parameters for Q119X mutants, compared with NDM-1, with some β-lactams

Substrate and parametera	NDM-1b	Q119C	Q119F	Q119E	Q119Y	Q119V	Q119K
Imipenem
kcat (s−1)	64	69	336	41	79	229	393
Km (μM)	35	50	157	40	30	65	90
kcat/Km (μM−1 s−1)	1.83	1.38	2.14	1.02	2.63	3.52	4.37
Meropenem
kcat (s−1)	75	252	1500	82	561	269	357
Km (μM)	80	100	252	146	105	20	37
kcat/Km (μM−1 s−1)	0.94	2.52	5.95	0.56	5.34	13.45	9.65
Benzylpenicillin
kcat (s−1)	105	100	166	100	34	231	414
Km (μM)	250	71	89	5c	8c	45	15
kcat/Km (μM−1 s−1)	0.42	1.41	1.86	20.0	4.25	5.10	27.6
Carbenicillin
kcat (s−1)	108	52	158	234	216	267	929
Km (μM)	285	59	131	18	31	32	35
kcat/Km (μM−1 s−1)	0.38	0.88	1.21	13.00	6.97	8.34	26.54
Cefazolin
kcat (s−1)	42	48	169	63	561	269	125
Km (μM)	20	11	27	4c	105	20	32
kcat/Km (μM−1 s−1)	2.10	4.36	6.26	15.75	5.34	13.45	3.90
Cefoxitin
kcat (s−1)	23	99	152	64	85	193	58
Km (μM)	26	23	21	23	17	18	49
kcat/Km (μM−1 s−1)	0.88	4.30	7.24	2.78	5.00	10.72	1.18
Cefotaxime
kcat (s−1)	20	43	59	4	7	21	89
Km (μM)	14	7c	6c	2c	2c	10c	3c
kcat/Km (μM−1 s−1)	1.43	6.14	9.83	2.00	3.50	2.00	29.67
Ceftazidime
kcat (s−1)	18.5	74	257	14	68	7	106
Km (μM)	50	163	403	140	2c	3c	11
kcat/Km (μM−1 s−1)	0.37	0.45	0.64	0.10	34.00	2.33	9.64
Cefepime
kcat (s−1)	13	22	67	18	30	71	60
Km (μM)	35	30	16	40	4c	10c	18
kcat/Km (μM−1 s−1)	0.37	0.73	4.19	0.45	7.50	7.10	3.33

^aEach kinetic value is the mean of five different measurements; the error was <5%.

^bKinetic data for NDM-1 were from reference 15.

^cK_m values were determined as K_i values, using nitrocefin as the reporter substrate (19).