L-Adrenaline belongs to a group of compounds known as catecholamines, which play an important role in the regulation of the physiological process in living organisms. In the present study, the inhibitory effect of L-adrenaline on lactoperoxidase was examined. Lactoperoxidase (E.C.184.108.40.206) was purified from bovine milk with three consecutive steps: Amberlite CG-50 resin, CM-Sephadex C-50 ion-exchange, and Sephadex G-100 gel filtration chromatography. Lactoperoxidase was purified with a yield of 42.18%, a specific activity of 30.33 EU/mg proteins, and 20.77 purification fold. Enzyme purity was determined with SDS-PAGE, where a single band was observed. The R-z (A(412)/A(280)) value for lactoperoxidase was 0.9. The effect of L-adrenaline on lactoperoxidase was determined using ABTS as a chromogenic substrate. The half maximal inhibitory concentration (IC50) value and an inhibition constant (K-i) values for L-adrenaline were 34.5 and 2.26 mu M, respectively. L-Adrenaline was found to be a non-competitive inhibitor.