Kinetic characterization, thermal and pH inactivation study of peroxidase and pectin methylesterase from tomato (Solanum betaceum)

Peroxidase (POD) and pectin methylesterase (PME) from tomato were characterized, studied thermal stability, and analyzed the synergistic effect of temperature and pH. For POD, the optimal activity, using H2O2 as substrate and ABTS(+center dot) as the donor H+, was obtained at pH 3.5, and for PME, the optimal activity using pectin as substrate was obtained at pH 7.5. In POD, it was found that the values of K-M, V-m and K-si for H2O2 were 477.26 mM, 721.53 mu M/min and 0.37 mM, respectively. In PME, the values of K-M and V-M obtained for pectin were 0.54 mM and 436.12 mu M/min, respectively. On the other hand, it was found that POD was inactivated with 90 degrees C, at pH from 2.5 to 3.5 with temperatures of 55 to 90 degrees C, and at pH of 2.5 to 3 with temperatures of 40 to 90 degrees C. Likewise, PME was inactivated at 90 degrees C, and at pH of 3.5 with 70 degrees C.