2h1u
From Proteopedia
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Porcine pancreatic elastase complexed with MetPheLeuGlu at pH 5.0
Overview
Although the subject of many studies, detailed structural information on, aspects of the catalytic cycle of serine proteases is lacking., Crystallographic analyses were performed in which an acyl-enzyme complex, formed from elastase and a peptide, was reacted with a series of, nucleophilic dipeptides. Multiple analyses led to electron density maps, consistent with the formation of a tetrahedral species. In certain cases, apparent peptide bond formation at the active site was observed, and the, electron density maps suggested production of a cis-amide rather than a, trans-amide. Evidence for a cis-amide configuration was also observed in, the noncovalent complex between elastase and an alpha1-antitrypsin-derived, tetrapeptide. Although there are caveats on the relevance of the, crystallographic data to solution catalysis, the results enable detailed, proposals for the pathway of the acylation step to be made. At least in, some cases, it is proposed that the alcohol of Ser-195 may preferentially, attack the carbonyl of the cis-amide form of the substrate, in a, stereoelectronically favored manner, to give a tetrahedral oxyanion, intermediate, which undergoes N-inversion and/or C-N bond rotation to, enable protonation of the leaving group nitrogen. The mechanistic, proposals may have consequences for protease inhibition, in particular for, the design of high energy intermediate analogues.
About this Structure
2H1U is a Single protein structure of sequence from Sus scrofa with CA and SO4 as ligands. Active as Pancreatic elastase, with EC number 3.4.21.36 Full crystallographic information is available from OCA.
Reference
Structural analyses on intermediates in serine protease catalysis., Liu B, Schofield CJ, Wilmouth RC, J Biol Chem. 2006 Aug 18;281(33):24024-35. Epub 2006 Jun 5. PMID:16754679
Page seeded by OCA on Wed Nov 21 11:30:12 2007
