Xylonolactonase from Caulobacter crescentus Is a Mononuclear Nonheme Iron Hydrolase

Johan Pääkkönen, Leena Penttinen, Martina Andberg, Anu Koivula, Nina Hakulinen, Juha Rouvinen, Janne Jänis (Corresponding Author)

Research output: Contribution to journalArticleScientificpeer-review

5 Citations (Scopus)


Caulobacter crescentus xylonolactonase (Cc XylC, EC 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 Ca2+, Zn2+, and Mg2+. 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 Fe2+ cation, specifically and with a high affinity (Kd = 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 Fe2+ 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.

Original languageEnglish
Pages (from-to)3046-3049
Number of pages4
Issue number41
Publication statusPublished - 19 Oct 2021
MoE publication typeA1 Journal article-refereed


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