Effects of some metals on paraoxonase activity from shark Scyliorhinus canicula.

Paraoxonase (PON) is an organophosphate hydrolyser enzyme which also has antioxidant properties in metabolism. Due to its crucial functions, the inhibition of the enzyme is undesirable and very dangerous. PON enzyme activity should not be altered in any case. Inhibitory investigations of this enzyme are therefore important and useful. Metal toxicology of enzymes has become popular in the recent years. Here, we report the in vitro inhibitory effects of some metal ions, including Ni(2+), Cd(2+), Cu(2+) and Hg(2+), on the activity of shark serum PON (SPON). For this purpose, we first purified the enzyme from shark Scyliorhinus canicula (LINNAEUS, 1758) serum and analysed the alterations in the enzyme activity in the presence of metal ions. The K(M) and V(max) is 0.227 mM and 454.545 U/mL, respectively. The results show that metal ions exhibit inhibitory effects on SPON1 at low concentrations with IC(50) values ranging from 0.29 to 2.00 mM. Copper was determined to be the most effective inhibitor with IC(50) of 0.29 mM.