Insights into Factors Affecting Lactoperoxidase Conformation Stability and Enzymatic Activity

Lactoperoxidase is a glycoprotein from the superfamily of mammalian haeme-containing peroxidases and has a great potential as a natural biopreservative in food and medicine due to its antimicrobial activity. For lactoperoxidase to be effectively utilised, its structural stability and consequently enzymatic activity must be maintained. Our measurements showed that two-state denaturation curve was observed at pH 3.5 and 4.0 in 100 mm buffers, whereas aggregation occurred at pH 5.0–7.0. Lactoperoxidase conformation stability was also affected by buffer type and buffer molar concentration and in presence of various ions (Ca2+, Mg2+, Na+). Furthermore, when lactoperoxidase was partially depleted of iron and calcium ions (de-LPO), thermal stability was lower in comparison with that of native lactoperoxidase and decreases in enzymatic activity were also observed. The enzymatic activity of lactoperoxidase was affected by the choice of buffer, pH, molar concentration of buffer, and temperature, but not by the presence of different ions.