Effect of Lead on Lactoperoxidase Enzyme Activity

Lact operoxidase (LPO) which is known as an antibacterial enzyme can be used as a biopreservative agent in many industrial products, such as foods, dairy products, cosmetics and drugs. Lead (Pb), a heavy methal with not any known physiological function in human body, is a persistent environment al toxin, and its adverse effects is seem yet. The aim of this study was to determine the effect of pb(2+) on the Lpo activity. Lpo activity was determined in the absence and presence of different concentrations of lead acetate, and Lineweaver-Burk reciprocal plot was drawn according to the data obtained. Pb2+ inhibited Lpo activity progressively up to concentration of 0.8 m M, where about 85% of the enzyme activity was lost. The inhibition was non -competitive with respect to 2,2- Azinobis [3-Ethyl Ben zothiazoline-6-sulphonic acid] diammonium salts (ABTS) as an enzyme substrate. It means that pb(2+) binds to other place than to the active site on the enzyme lead to a conformational change of the enzyme, so that the catalytic activity of the enzyme is decreased. Our data represented that pb(2+) reversibly inhibited LPO activity by non-competitive inhibition pattern. Also, conformational change upon pb(2+) binding can decrease the antibacterial property of the enzyme where it is used as a biopreservative.