| 18406355 |
van Loo B, Permentier HP, Kingma J, Baldascini H, Janssen DB: Inactivation of epoxide hydrolase by catalysis-induced formation of isoaspartate. FEBS Lett. 2008 May 14;582(11):1581-6. Epub 2008 Apr 10.
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 para-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 para-nitrostyrene epoxide, indicating that it is related to the structure of the covalent hydroxyalkyl-enzyme intermediate. |
34(0,1,1,4) |