Structure of tyrosinase from walnut (juglans regia)
Structure:
Polyphenol oxidase. Chain: a, b
Source:
Juglans regia. English walnut. Organism_taxid: 51240
Resolution:
1.80Å
R-factor:
0.171
R-free:
0.188
Authors:
A.Bijelic,M.Pretzler,F.Zekiri,A.Rompel
Key ref:
A.Bijelic
et al.
(2015).
The Structure of a Plant Tyrosinase from Walnut Leaves Reveals the Importance of "Substrate-Guiding Residues" for Enzymatic Specificity.
Angew Chem Int Ed Engl,
54,
14677-14680.
PubMed id: 26473311
DOI: 10.1002/anie.201506994
Tyrosinases and catechol oxidases are members of the class of type III copper
enzymes. While tyrosinases accept both mono- and o-diphenols as substrates, only
the latter substrate is converted by catechol oxidases. Researchers have been
working for decades to elucidate the monophenolase/diphenolase specificity on a
structural level and have introduced an early hypothesis that states that the
reason for the lack of monophenolase activity in catechol oxidases may be its
structurally restricted active site. However, recent structural and biochemical
studies of this enzyme class have raised doubts about this theory. Herein, the
first crystal structure of a plant tyrosinase (from Juglans regia) is presented.
The structure reveals that the distinction between mono- and diphenolase
activity does not depend on the degree of restriction of the active site, and
thus a more important role for amino acid residues located at the entrance to
and in the second shell of the active site is proposed.
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