Submitted to: Plant Physiology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 10, 1996
Publication Date: N/A
Interpretive Summary: With the increased popularity of Spanish cuisine, pungent pepper production is becoming a more economically important crop in the southwestern U.S. Enzymes involved in the ripening of pepper fruit are important to future breeding programs, because of their potential manipulation in enhancing or decreasing ripening, increasing disease resistance, and enhancing flavor quality. Peroxidase is an enzyme that has been implicated in playing a role in disease resistance, and possibly, flavor quality in pungent peppers. The research conducted, showed that peroxidases increased as the pepper ripened. An acidic peroxidase was characterized according to molecular weight, isoelectric charge, optimum pH, and temperature range. These characteristics are needed for further purification and isolation of peroxidase genes.
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 (Biles et al., 1993). 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 0C 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.