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Continuous Spectrophotometric Method for Determining Monophenolase and Diphenolase Activities of Pear Polyphenoloxidase
Author(s) -
ESPÍN JUAN CARLOS,
MORALES MERCEDES,
VARÓN RAMÓN,
TUDELA JOSÉ,
GARCÍACÁNOVAS FRANCISCO
Publication year - 1996
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1365-2621.1996.tb10955.x
Subject(s) - chemistry , adduct , hydrazone , polyphenol oxidase , quinone , solubility , nuclear chemistry , chromatography , organic chemistry , enzyme , peroxidase
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.