TABLE 3.

Kinetic parameters of purified CME-1 enzyme

Substrate	Km (μM)ab	kcat (s−1)a	kcat/Km (μM−1 s−1)
Penicillin G	3.1 ± 0.2	1.2 ± 0.07	0.39
Ampicillin	5.1 ± 0.4	2.9 ± 0.18	0.57
Carbenicillin	7.0 ± 0.4	2.6 ± 0.17	0.37
Piperacillin	0.12 ± 0.01	0.23 ± 0.02	1.92
Nitrocefin	25 ± 1.2	134 ± 8.0	5.36
Cephaloridine	87 ± 5.7	74 ± 4.3	0.85
Cephalothin	105 ± 4.4	118 ± 6.0	1.12
Cefuroxime	106 ± 4.6	102 ± 6.2	0.96
Cefoxitin	NDc	NHd
Cefotaxime	50 ± 3.0	27 ± 1.6	0.54
Ceftazidime	511 ± 36	68 ± 4.4	0.13
Cefepime	487 ± 39	48 ± 2.7	0.099
Imipenem	ND	NH
Aztreonam	5.0 ± 0.3	0.23 ± 0.02	0.046
Carumonam	3.6 ± 0.3	0.17 ± 0.01	0.047

^aValues are means ± standard deviations of three measurements. 

^bDetermined as K_i when K_m was lower than 10 μM. 

^cnot determined. 

^dNH, no hydrolysis detected.