Continuous Spectrophotometric Method for Determining Monophenolase and Diphenolase Activities of Pear Polyphenoloxidase

A continuous spectrophotometric method was based on the coupling reaction between 3-methyl-2-benzothiazolinone hydrazone (MBTH) and the quinone product of the oxidation of p-hydroxyphenyl propionic acid (PHPPA) or 3,4-dihydroxyphenyl propionic acid (DHPPA) in the presence of polyphenol oxidase. The...
Ausführliche Beschreibung

A continuous spectrophotometric method was based on the coupling reaction between 3-methyl-2-benzothiazolinone hydrazone (MBTH) and the quinone product of the oxidation of p-hydroxyphenyl propionic acid (PHPPA) or 3,4-dihydroxyphenyl propionic acid (DHPPA) in the presence of polyphenol oxidase. The monophenolase activity of pear PPO was characterized for the first time. Solubility and stability of the adduct formed at the optimum pH (4.3) enabled the system to reach steady-state, making it possible to determine monophenolase activity with short lag periods. This, together with the value of ε for the MBTH-quinone adduct, makes this method more sensitive than other continuous methods for assaying monophenolase and diphenolase activities. Ausführliche Beschreibung