Purification and kinetic characterization of peroxidase from tomato cultivated under different salinity conditions

By including hydrophobic chromatography in the purification scheme, 2 homog eneous tomato fruit peroxidase isoenzymes were obtained. The expression of these 2 peroxidases, one acid and the other basic, was determined in tomato fruits grown under different salinity conditions. Increased salinity modif ied the isoenzyme profile of tomato peroxidase. In tomatoes grown under hig hly saline conditions, there was an increase in the expression of the acid form with respect to the basic, the acid/basic ratio rising from 4.5 in tom atoes grown under normal saline conditions to 70 in those grown in highly s aline conditions. Kinetic studies using 2,2'-azinobis(3-ethylbenzo-thiazoli nesulfonic acid) as reducing substrate showed that increased salinity in th e growth medium did not modify the kinetic parameter of tomato peroxidase o ver both hydrogen peroxide or reducing substrate.