TABLE 3.

Kinetic parameters of purified β-lactamase OXA-69^a

Substrate	kcat (10−3 s−1)	Km (μM)	kcat/Km (10−3 mM−1 · s−1)	kcat/Km (%)b
Benzylpenicillin	200	710	300	100
Ampicillin	60	240	250	85
Ticarcillin	300	2,800	110	40
Piperacillin	200	4,000	50	20
Nitrocefin	400	130	3,200	1,100
Cephalothin	4	190	20	7
Cephaloridine	50	2,500	20	7
Ceftazidime	NDc
Cefepime	ND
Aztreonam	ND
Imipenem	100	3,600	30	10
Meropenem	60	4,500	10	3
Oxacillin	200	3,700	60	20

^aData are the means of three independent experiments. Standard deviations were within 10% of the means.

^bPercentage is calculated as compared to that of benzylpenicillin, taken as 100%.

^cND, no detectable hydrolysis (<0.01 s⁻¹).