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Characterization of Polyphenol Oxidase from Airen Grapes
Author(s) -
VALERO EDELMIRA,
VARÓN RAMÓN,
GARCÍACARMONA FRANCISCO
Publication year - 1988
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.1365-2621.1988.tb09304.x
Subject(s) - polyphenol oxidase , chemistry , substrate (aquarium) , enzyme , food science , catechol oxidase , polyphenol , enzyme assay , enzyme kinetics , lag time , oxidase test , nuclear chemistry , biochemistry , active site , biology , antioxidant , peroxidase , ecology , biological system
Polyphenol oxidase (PPO) was isolated from grapes grown in Spain and its characteristics were studied. The partially purified enzyme had both cresolase and catecholase activities. Catecholase activity had a pH optimum in a range 3.5–4.5 and was characterized by a relatively high stability to heat. The apparent K M for 4‐methylcatechol was 9.5 mM. Cresolase activity presents a lag period which is modulated by different factors: enzyme concentration, substrate concentration, temperature or pH. The presence of o‐diphenols in the reaction medium abolishes the lag period, these acting as co‐substrates. The apparent K M towards p‐cresol and the activation constant for o‐diphenol for cresolase activity were 0.35 mM and 1.75 μM, respectively.