Characterization of polyphenol oxidase from purple sweet potato (Ipomoea batatas L. Lam) and its affinity towards acylated anthocyanins and caffeoylquinic acid derivatives

Biochemical characterization of polyphenol oxidase (PPO) present in purple sweet potato (PSP) is a key step in developing efficient methodologies to control oxidative damage caused by this enzyme to the valuable components of PSP, such as caffeoylquinic acid derivatives and acylated anthocyanins. Thus, this work focused on the assessment of the effects of pH, temperature, and chemical agents on the PPO activity as well as characterization of the PPO substrate specificity towards major phenolic compounds found in PSP. The optimum conditions of enzyme activity were pH 7 and a temperature range of 20-30 degrees C at which phenolic substrates were oxidized with 72.5-99.8% yield. Zn2+ ions remarkably reduced PPO activity while Cu2+ ions improved enzyme performance. The highest substrate preference was shown for 3,4,5-tri-caffeoylquinic and 3,5-di-caffeoylquinic acid, followed by 5-caffeoylquinic and caffeic acid, 3,4- and 4,5-di-caffeoylquinic acids, peonidin-3-caffeoyl-p-hydroxybenzoylsophoroside-5-glucoside. The highest Km values were found for 4,5-feruloyl-caffeoylquinic acid and catechol.

Automated summary

This study focused on assessing the effects of pH, temperature, and chemical agents on PPO activity, as well as characterizing the substrate specificity of PPO towards major phenolic compounds found in purple sweet potato. The optimal conditions for enzyme activity were found to be pH 7 and a temperature range of 20-30 degrees Celsius, resulting in oxidation yields of 72.5-99.8% for phenolic substrates.