TABLE 3.

Kinetic properties of the SHV-13 enzyme from K. pneumoniae 803

Substrate	Km (μM)	Relative Vmaxa of SHV-13 (%)	Vmax/Kma ratio	Relative Vmaxa of SHV-1 (%)d
Benzylpenicillin	10	100	100	100
Ampicillin	28	178	64	150
Piperacillin	18	136	76
Oxacillin	NDb	NLKc	ND	<0.5
Cephaloridine	97	176	18	48
Cefuroxime	61	11	1.8	ND
Ceftriaxone	11	12	11	ND
Cefotaxime	52	27	5.2	0.18
Ceftazidime	91	0.38	0.42	0.02
Cefoxitin	ND	<0.1	ND	0
Aztreonam	77	0.66	0.86	<0.38
Imipenem	ND	<0.1	ND	ND

^aRelative to that for benzylpenicillin, which was set at 100%. 

^bND, not determined. 

^cNLK, nonlinear kinetics. 

^dFrom reference 2.