Purification and partial characterization of peroxidase from lettuce stems

Peroxidase (EC1.11.1.7) was purified to homogeneity from lettuce ( Lactuca sativa L.) stems by means of 40 to 80% ammonium sulfate precipitation, Sephadex G-100 gel filtration and affinity chromatography with concanavalin A. Peroxidase was purified 17.92-fold with 2.67% recovery and its molecular mass was 35 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Its optimum temperature and pH were 45°C and 5.0. In addition, it showed moderate thermostability at 60°C. Its K m for guaiacol, pyrogallol, 2, 2’-azino-bis-(3-ethylbenzthiazolin-6-sulfonate) and catechol was 4.74, 1.96, 3.75 and 2.95 mM, respectively. Its activity was inhibited by metal ions (Fe 3+ , Zn 2+ , Ca 2+ , Cu 2+ and Mn 2+ ) and organic solvents (methyl alcohol, ethanol and acetone). Key words: Lettuce, partial characterization, peroxidase, protein purification, thermostability.