Open AccessXylonolactonase from Caulobacter crescentus Is a Mononuclear Nonheme Iron Hydrolase
Author(s) -
Johan Pääkkönen,
Leena Penttinen,
Martina Andberg,
Anu Koivula,
Nina Hakulinen,
Juha Rouvinen,
Janne Jänis
Publication year - 2021
Publication title -
biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.43
H-Index - 253
eISSN - 1520-4995
pISSN - 0006-2960
DOI - 10.1021/acs.biochem.1c00249
Subject(s) - chemistry , hydrolysis , stereochemistry , bivalent (engine) , intramolecular force , lactone , metal , isomerization , metal ions in aqueous solution , enzyme , catalysis , medicinal chemistry , biochemistry , organic chemistry
Caulobacter crescentus xylonolactonase ( Cc XylC, EC 3.1.1.68) catalyzes an intramolecular ester bond hydrolysis over a nonenzymatic acid/base catalysis. Cc XylC is a member of the SMP30 protein family, whose members have previously been reported to be active in the presence of bivalent metal ions, such as Ca 2+ , Zn 2+ , and Mg 2+ . By native mass spectrometry, we studied the binding of several bivalent metal ions to Cc XylC and observed that it binds only one of them, namely, the Fe 2+ cation, specifically and with a high affinity ( K d = 0.5 μM), pointing out that Cc XylC is a mononuclear iron protein. We propose that bivalent metal cations also promote the reaction nonenzymatically by stabilizing a short-lived bicyclic intermediate on the lactone isomerization reaction. An analysis of the reaction kinetics showed that Cc XylC complexed with Fe 2+ can speed up the hydrolysis of d-xylono-1,4-lactone by 100-fold and that of d-glucono-1,5-lactone by 10-fold as compared to the nonenzymatic reaction. To our knowledge, this is the first discovery of a nonheme mononuclear iron-binding enzyme that catalyzes an ester bond hydrolysis reaction.