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Inactivation of epoxide hydrolase by catalysis‐induced formation of isoaspartate
Author(s) -
van Loo Bert,
Permentier Hjalmar P.,
Kingma Jaap,
Baldascini Helen,
Janssen Dick B.
Publication year - 2008
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2008.04.001
Subject(s) - chemistry , epoxide , epoxide hydrolase , stereochemistry , nucleophile , residue (chemistry) , enzyme , hydrolase , epoxide hydrolase 2 , enantiomer , catalysis , biochemistry , microsome
Epoxide hydrolases catalyze hydrolytic epoxide ring‐opening, most often via formation of a covalent hydroxyalkyl‐enzyme intermediate. A mutant of Agrobacterium radiobacter epoxide hydrolase, in which the phenylalanine residue that flanks the invariant catalytic aspartate nucleophile is replaced by a threonine, exhibited inactivation during conversion when the ( R )‐enantiomer of p ‐nitrostyrene epoxide was used as substrate. HPLC analysis of tryptic fragments of the epoxide hydrolase, followed by MALDI‐TOF and TOF/TOF analysis, indicated that inactivation was due to conversion of the nucleophilic aspartate into isoaspartate, which represents a novel mechanism of catalysis‐induced autoinactivation. Inactivation occurred at a lower rate with the ( S )‐enantiomer of p ‐nitrostyrene epoxide, indicating that it is related to the structure of the covalent hydroxyalkyl‐enzyme intermediate.