X-ray snapshots of serine protease catalysis reveal a tetrahedral intermediate

Citation
Rc. Wilmouth et al., X-ray snapshots of serine protease catalysis reveal a tetrahedral intermediate, NAT ST BIOL, 8(8), 2001, pp. 689-694
Citations number
31
Categorie Soggetti
Biochemistry & Biophysics
Journal title
NATURE STRUCTURAL BIOLOGY
ISSN journal
10728368 → ACNP
Volume
8
Issue
8
Year of publication
2001
Pages
689 - 694
Database
ISI
SICI code
1072-8368(200108)8:8<689:XSOSPC>2.0.ZU;2-8
Abstract
Studies on the catalytic mechanism and inhibition of serine proteases are w idely used as paradigms for teaching enzyme catalysis. Ground-breaking work on the structures of chymotrypsin and subtilisin led to the idea of a cons erved catalytic triad formed by the active site Ser, His and Asp residues. An oxyanion hole, consisting of the peptide amide of the active site serine and a neighbouring glycine, was identified, and hydrogen bonding in the ox yanion hole was suggested to stabilize the two proposed tetrahedral interme diates on the catalytic pathway. Here we show electron density changes cons istent with the formation of a tetrahedral intermediate during the hydrolys is of an acyl-enzyme complex formed between a natural heptapeptide and elas tase. No electron density for an enzyme-product complex was observed. The s tructures also suggest a mechanism for the synchronization of hydrolysis an d peptide release triggered by the conversion of the sp(2) hybridized carbo nyl carbon to an sp(3) carbon in the tetrahedral intermediate. This affects the location of the peptide in the active site deft, triggering the collap se of a hydrogen bonding network between the peptide and the P-sheet of the active site.