Characterization of chile pepper fruit peroxidases during ripening

The enzymatic levels of peroxidases were found to increase in chile pepper fruit during ripening. Previous work indicated that peroxidases were associated with the cuticle of the fruit where the enzymatic levels correlated with cuticle thickening and disease resistance. Fruit harvested at intervals throughout the growing season showed incremental increases in total peroxidase enzyme levels and increased intensity in the activity of an acidic isozyme form of pl = 4.0 in polyacrylamide gels. Fast protein liquid chromatography on an anion-exchange column yielded an acidic peroxidase enzyme activity in both green and red chile fruits. This peroxidase was purified 75-fold. The fraction of peroxidase activity in a 28.3 kDa form increased from immature green to fully ripened red fruits, and it dominated in fully ripened red chile fruits. This activity was markedly stable in in vitro incubations up to 60 C for 15 min. Similar incubations above 70°C decreased peroxidase activity. The optimal pH for fruit peroxidase enzymatic activity was 6 with nearly equivalent stability over the range for 6-8. These results indicate that alternate forms of chile fruit peroxidases vary during fruit ripening, are stable at elevated temperatures, and demonstrate broad pH optima during the ripening stages.