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Modelling the effect of superatmospheric oxygen concentrations on in vitro mushroom PPO activity
Author(s) -
Gómez Perla A,
Geysen Sabine,
Verlinden Bert E,
Artés Francisco,
Nicolaï Bart M
Publication year - 2006
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.2629
Subject(s) - uncompetitive inhibitor , chemistry , oxygen , michaelis–menten kinetics , non competitive inhibition , substrate (aquarium) , reaction rate constant , limiting oxygen concentration , kinetics , product inhibition , polyphenol oxidase , browning , nuclear chemistry , stereochemistry , biochemistry , enzyme , enzyme assay , organic chemistry , peroxidase , biology , ecology , physics , quantum mechanics
The kinetics of polyphenol oxidase (PPO, EC 1.14.18.1) with respect to oxygen concentrations from 5 to 100% using chlorogenic acid (CGA) as substrate was examined. In vitro mushroom PPO activity was determined by measuring the consumption of oxygen during the oxidation reaction. A differential Michaelis–Menten model was fitted to the obtained total depletion curves. The product concentration as well as the concentration of oxygen had a clear inhibitory effect on the reaction rate. However, the inhibitory effect of oxygen was more evident at low product concentration. A linear mixed inhibition model that considered both the product (oxidised CGA) and oxygen as inhibitors was developed. A model with the product as a competitive inhibitor and oxygen as an uncompetitive inhibitor was the most appropriate to explain the reaction kinetics. The values of the inhibition constants calculated from the model were 0.0032 mmol L −1 for K m (Michaelis–Menten constant related to oxygen), 0.023 mmol L −1 for K mc (constant for competitive inhibition due to the product), 1.630 mmol L −1 for K mu (constant for uncompetitive inhibition due to oxygen) and 1.77 × 10 −4 mmol L −1 s −1 for V max (maximum reaction rate). The results indicate that superatmospheric oxygen concentrations could be effective in preventing enzymatic browning by PPO. Copyright © 2006 Society of Chemical Industry