Table 3.

Kinetic parameters and inhibition profile of SMB-1^a

Substrate or chelating agent	Km (μM)	kcat (s−1)	kcat/Km (M−1·s−1)	Relative kcat/Kmd	IC50 (μM)
Ampicillin	102	247	2.4 × 106	100
Piperacillin	380	68	1.8 × 105	7.5
Cephalothin	15	28	1.9 × 106	79
Cefuroxime	22	30	1.4 × 106	58
Cefotaxime	35	31	8.9 × 105	37
Ceftazidime	57	4.4	7.7 × 104	3.2
Cefepime	747	2.7	3.6 × 103	0.15
Cefoxitin	26	39	1.5 × 106	63
Aztreonam	NHb	NDc	ND	ND
Imipenem	133	518	3.9 × 106	163
Meropenem	144	604	4.2 × 106	175
Dipicolinic acid					2.2
1,10-o-Phenanthroline					156
EDTA					14

^aStandard deviations for each parameter were below 10%.

^bNH, no measurable hydrolysis detected with 1 μM enzyme.

^cND, not determined.

^dRelative k_cat/K_m value was expressed compared to that of ampicillin, which was assigned 100.