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Selenocysteine as a Substrate, an Inhibitor and a Mechanistic Probe for Bacterial and Fungal Iron‐Dependent Sulfoxide Synthases
Author(s) -
Goncharenko Kristina V.,
Flückiger Sebastian,
Liao Cangsong,
Lim David,
Stampfli Anja R.,
Seebeck Florian P.
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201903898
Subject(s) - sulfoxide , substrate (aquarium) , chemistry , selenocysteine , substrate specificity , biochemistry , stereochemistry , enzyme , biology , organic chemistry , ecology , cysteine
Sulfoxide synthases are non‐heme iron enzymes that participate in the biosynthesis of thiohistidines, such as ergothioneine and ovothiol A. The sulfoxide synthase EgtB from Chloracidobacterium thermophilum ( Cth EgtB) catalyzes oxidative coupling between the side chains of N ‐α‐trimethyl histidine (TMH) and cysteine (Cys) in a reaction that entails complete reduction of molecular oxygen, carbon–sulfur (C−S) and sulfur–oxygen (S−O) bond formation as well as carbon–hydrogen (C−H) bond cleavage. In this report, we show that Cth EgtB and other bacterial sulfoxide synthases cannot efficiently accept selenocysteine (SeCys) as a substrate in place of cysteine. In contrast, the sulfoxide synthase from the filamentous fungus Chaetomium thermophilum ( Cth Egt1) catalyzes C−S and C−Se bond formation at almost equal efficiency. We discuss evidence suggesting that this functional difference between bacterial and fungal sulfoxide synthases emerges from different modes of oxygen activation.