TABLE 2.

Kinetic and inhibition parameters of the OXA-24 β-lactamase^a

Antibiotic	Km (μM)	Vmax (μmol/min/μl)	Relative Vmax/Kmb	Relative hydrolysis rateb	IC50 (μM)c
Benzylpenicillin	65	370	100	100
Cephaloridine	395	200	9	64
Oxacillin	NDd	ND	ND	<1
Cloxacillin	ND	ND	ND	<1
Methicillin	ND	ND	ND	<1
Imipenem	20	15	13	4
Meropenem	775	280	6	2
Clavulanic acid					50
Sulbactam					40
Tazobactam					0.5

^aKinetic experiments were performed using a protein extract with a specific activity of 13.61 μmol of nitrocefin hydrolyzed/min/μg of protein. 

^bObtained by normalizing the value of each antibiotic to that for benzylpenicillin (taken as 100). 

^cNitrocefin was used as the substrate (25 μg/ml) following 10 min of preincubation of enzyme and inhibitor. 

^dND, hydrolysis not detected.