TABLE 5.

Metal/enzyme ratios and catalytic efficiencies of the metallo-β-lactamase at different pH values^a

pH	Buffer	[Zn]/[enzyme]	kcat/Km (μM−1 s−1)
5	Acetate	1.8 ± 0.2	0.8
5	Citrate	0.3 ± 0.1	<0.01
6	Cacodylate	1.9 ± 0.2	1
6.5	Cacodylate	1.8 ± 0.2	1.2
7	Cacodylate	1.9 ± 0.2	1.2
7.5	HEPES	1.7 ± 0.2	1.2
8	HEPES	1.8 ± 0.2	0.5

^aThe substrate was imipenem.