Premium
Tyrosinase versus Catechol Oxidase: One Asparagine Makes the Difference
Author(s) -
Solem Even,
Tuczek Felix,
Decker Heinz
Publication year - 2016
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201508534
Subject(s) - tyrosinase , catechol , asparagine , hydroxylation , catechol oxidase , chemistry , deprotonation , biochemistry , stereochemistry , enzyme , oxidase test , organic chemistry , polyphenol oxidase , peroxidase , ion
Tyrosinases mediate the ortho ‐hydroxylation and two‐electron oxidation of monophenols to ortho ‐quinones. Catechol oxidases only catalyze the oxidation of diphenols. Although it is of significant interest, the origin of the functional discrimination between tyrosinases and catechol oxidases has been unclear. Recently, it has been postulated that a glutamate and an asparagine bind and activate a conserved water molecule towards deprotonation of monophenols. Here we demonstrate for the first time that a polyphenoloxidase, which exhibits only diphenolase activity, can be transformed to a tyrosinase by mutation to introduce an asparagine. The asparagine and a conserved glutamate are necessary to properly orient the conserved water in order to abstract a proton from the monophenol. These results provide direct evidence for the crucial importance of a proton shuttle for tyrosinase activity of type 3 copper proteins, allowing a consistent understanding of their different chemical reactivities.