Table 9.

Effect of metals on esterase activity^a

Metalb	Specific activity (μmol/min/mg)	% Control
Controlc	26.4 ± 0.7	100
Barium	29.0 ± 3.4	110
Cerium(III)	28.2 ± 2.3	107
Cesium	27.4 ± 1.4	104
Calcium	27.6 ± 1.8	104
Lithium	27.5 ± 0.4	104
Copper(I)	27.1 ± 3.3	103
Manganese	26.6 ± 1.7	101
Cadmium	26.0 ± 1.0	98
Cobalt	25.7 ± 1.5	97
Lead(II)	25.7 ± 0.9	97
Mercury	25.4 ± 0.2	96
Iron(III)	24.0 ± 0.5	91*
Potassium	23.8 ± 3.4	90
Zinc	23.3 ± 1.0	88*
Rubidium	23.3 ± 0.1	88*
Sodium	22.2 ± 4.2	84
Nickel	19.5 ± 1.0	74*
Iron(II)	19.1 ± 2.6	72*
Copper(II)	18.2 ± 2.5	69*
Diazinon-oxon	0.01 ± 0.0	0

^aAssays were performed in quadruplicate using the liquid esterase preparation (lot 102K7062; Sigma Chemical, St. Louis, MO, USA). Activity assays were performed with the substrate p-nitrophenyl acetate. An asterisk indicates that the value is significantly lower than control using Student’s t test (p < 0.05).

^bAll metals were purchased as the chloride salt and were present at a final concentration of 1 mM.

^cControl is defined as the activity measured in sodium phosphate buffer (0.1 M, pH 7.4, 25°C) in the absence of any metals.