TABLE 3.

β-Lactamase activities and clavulanate and tazobactam IC₅₀s for TEM-1 β-lactamase and TEM mutant enzymes

Amino acid change from TEM-1a	Designation	β-Lactamase activityb	IC50 (μM)
			Clavulanate	Tazobactam
TEM-1	TEM-1	5,330	0.08	0.03
M69L	TEM-33	586	2	0.5
M69L, N276D	TEM-35	1,190	12	0.6
R244C	TEM-31	514	10	1.7
G238S	TEM-19	2,950	0.001	0.002
G238S, M69L		853	0.03	0.02
G238S, M69L, N276D		2,360	0.38	0.04
G238S, R244C		485	1.5	0.3
G238S, E104K	TEM-15	29	0.002	0.004
G238S, E104K, M69L		319	0.07	0.01
G238S, E104K, M69L, N276D	TEM-50	952	0.3	0.02
G238S, E104K, R244C		696	1.1	1.2
R164S	TEM-12	25	0.02	0.02
R164S, M69L		49	0.25	0.2
R164S, M69L, N276D		1,440	1.8	0.3
R164S, R244C		937	4.5	5
R164S, E104K	TEM-26	523	<0.01	0.06
R164S, E104K, M69L		211	0.08	0.3
R164S, E104K, M69L, N276D		458	0.35	0.2
R164S, E104K, R244C		54	3.5	2

^aSee footnote a to Table 2 for a key to the amino acid substitutions. 

^bActivities are expressed as nanomoles of nitrocefin hydrolyzed per minute per milligram of protein.