A New Member of the Alkaline Phosphatase Superfamily with a Formylglycine Nucleophile: Structural and Kinetic Characterisation of a Phosphonate Monoester Hydrolase/Phosphodiesterase from Rhizobium leguminosarum

Stefanie Jonas, Bert van Loo, Marko Hyvönen*, Florian Hollfelder

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

51 Citations (Scopus)

Abstract

The alkaline phosphatase superfamily comprises a large number of hydrolytic metalloenzymes such as phosphatases and sulfatases. We have characterised a new member of this superfamily, a phosphonate monoester hydrolase/phosphodiesterase from Rhizobium leguminosarum (RlPMH) both structurally and kinetically. The 1.42 Å crystal structure shows structural homology to arylsulfatases with conservation of the core α/β-fold, the mononuclear active site and most of the active-site residues. Sulfatases use a unique formylglycine nucleophile, formed by posttranslational modification of a cysteine/serine embedded in a signature sequence (C/S)XPXR. We provide mass spectrometric and mutational evidence that RlPMH is the first non-sulfatase enzyme shown to use a formylglycine as the catalytic nucleophile. RlPMH hydrolyses phosphonate monoesters and phosphate diesters with similar efficiency. Burst kinetics suggest that substrate hydrolysis proceeds via a double-displacement mechanism. Kinetic characterisation of active-site mutations establishes the catalytic contributions of individual residues. A mechanism for substrate hydrolysis is proposed on the basis of the kinetic data and structural comparisons with E. coli alkaline phosphatase and Pseudomonas aeruginosa arylsulfatase. RlPMH represents a further example of conservation of the overall structure and mechanism within the alkaline phosphatase superfamily.

Original languageEnglish
Pages (from-to)120-136
Number of pages17
JournalJournal of Molecular Biology
Volume384
Issue number1
Early online date4 Sep 2008
DOIs
Publication statusPublished - 5 Dec 2008
Externally publishedYes

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