Table 1.

Metal/enzyme ratio and activity at pH 7.0 of pneumococcal Pce purified in 3 μM ZnCl2 containing buffers

	Activity (%)a			Cation/Pce ratiob
Dialysis buffer	HEPESc	HEPES 10 μM Zn2+	HEPES 3 mM EDTA	Zn2+	Ca2+
HEPES	100	100	100	2.0	2.1
HEPES 3 μM Zn2+	100	100	100	2.0	2.1
HEPES 10 μM Zn2+	100	100	100	2.2	2.2
HEPES 3 mM EDTA	40	90	40	0.66	1.7

^a Whenever necessary, Pce samples were previously re-equilibrated in the buffer used for kinetic assays to avoid possible interferences.

^b Cation/protein stoichiometries were measured by ICP-OE in the dialysis buffer (~10 μM Pce), and estimated errors are < 5%.

^c Buffer A.