Allantoinase in lake trout (Salvelinus namaycush): In vitro effects of PCBs, DDT and metals

1. Allantoinase, an enzyme in the purine-urea cycle, was found in livers of Salvelinus namaycush (Osteichthyes: Salmoniformes).

2. The enzyme was active from pH 6.6 to 8.2 at 37°C and from pH 7.4 to 9.0 at 10°C and had an Arrhenius energy was activation of 11.0 kcal/mol and a temperature quotient of 2.0. The K_m of the enzyme homogenate was 8.4 mM allantoin.

3. The concentrations of inorganic metals at which 50% inhibition occurred during in vitro exposure were 6.0 mg/l Cu²⁺, 6.7 mg/l Cd²⁺, 34 mg/l Hg²⁺ and 52 mg/l Pb²⁺. The in vitro sensitivity to PCBs, DDT and DDE and kinetics in the presence of metals were determined.

4. Allantoinase activity was negatively correlated with body length for fish from Lake Michigan but not from Lake Superior or the laboratory.