Abstract Immobilized oxidases were bound on the surface of an affinity membrane and mounted on an oxygen electrode. These biosensors were used for heavy metal salt measurements. After immobilization on the enzymes, first order kinetics of inactivation were observed. Surface immobilization increases the sensitivity by a factor of 10, compared to reticulation of the enzyme in a gelatin matrix. After immobilization, 50% inactivation was observed with 20 μ m HgCl 2 for L-glycerophosphate oxidase and 50 n m for pyruvate oxidase. Restoration of activity after HgCl 2 treatment is feasible, but neither complete nor reproducible. To reuse the biosensor, L-lactate dehydrogenase (LDH) from rabbit muscle in solution was coupled to immobilized L-lactate oxidase (insensitive to heavy metal salts). LDH (particularly inexpensive) was replaced after each measurement. The I 50 in phosphate buffer was 1 μ m for HgCl 2 and 0·1 μ m for AgNO 3 ; with other heavy metal salts, no inhibition was observed below 500 μ m . In Tris buffer, the I 50 was 10 μ m for CdCl 2 and ZnCl 2 , 50 μ m for Pb-acetate and 250 μ m for CuSO 4 . The use of different enzymes and buffers may allow measurement of specific heavy metal salts.
[1]
C. Tran-Minh,et al.
Immobilized Enzyme Probes for Determining Inhibitors
,
1985
.
[2]
M. Chiba,et al.
Inhibition Mechanisms of δ-Aminolevulinic Acid Dehydratase by Heavy Metals
,
1988
.
[3]
A. M. Zapata-Bacri,et al.
Enzyme electrode composed of the pyruvate oxidase from Pediococcus species coupled to an oxygen electrode for measurements of pyruvate in biological media.
,
1987,
Biosensors.
[4]
B Danielsson,et al.
Enzyme thermistor analysis of heavy metal ions with use of immobilized urease
,
1978,
FEBS letters.
[5]
John Leyden. Webb,et al.
Enzyme and metabolic inhibitors
,
1963
.