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1e34
From Proteopedia
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==Overview== | ==Overview== | ||
| - | beta-Lactams inhibit a range of enzymes via acylation of nucleophilic | + | beta-Lactams inhibit a range of enzymes via acylation of nucleophilic serine residues. Certain gamma-lactam analogues of monocyclic beta-lactams have also been shown to be reversible inhibitors of porcine pancreatic elastase (PPE), forming acyl-enzyme complexes that are stable with respect to hydrolysis. Crystallographic analysis at pH 5 of an acyl-enzyme complex formed with PPE and one of these inhibitors revealed the ester carbonyl located in the oxyanion hole in a similar conformation to that observed in the structure of a complex formed between a heptapeptide (beta-casomorphin-7) and PPE. Only weak electron density was observed for the His-57 side chain in its 'native' conformation. Instead, the His-57 side chain predominantly adopted a conformation rotated approx. 90 degrees from its normal position. PPE-gamma-lactam crystals were subjected to 'pH-jumps' by placing the crystals in a buffer of increased pH prior to freezing for data collection. The results indicate that the conformation of the gamma-lactam-derived acyl-enzyme species in the PPE active site is dependent on pH, a result having implications for the analysis of other serine protease-inhibitor structures at non-catalytic pH values. The results help to define the stereoelectronic relationship between the ester of the acyl-enzyme complex, the side chain of His-57 and the incoming nucleophile during the reversible (de)acylation steps, implying it is closely analogous to the hydrolytic deacylation step during catalytic peptide hydrolysis. |
==About this Structure== | ==About this Structure== | ||
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[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: Sus scrofa]] | [[Category: Sus scrofa]] | ||
| - | [[Category: Clifton, I | + | [[Category: Clifton, I J.]] |
| - | [[Category: Schofield, C | + | [[Category: Schofield, C J.]] |
| - | [[Category: Wilmouth, R | + | [[Category: Wilmouth, R C.]] |
| - | [[Category: Wright, P | + | [[Category: Wright, P A.]] |
[[Category: CA]] | [[Category: CA]] | ||
[[Category: SO4]] | [[Category: SO4]] | ||
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[[Category: serine proteinase]] | [[Category: serine proteinase]] | ||
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:23:15 2008'' |
Revision as of 10:23, 21 February 2008
|
PORCINE PANCREATIC ELASTASE COMPLEXED WITH (3S, 4S)N-PARA-TOLUENESULPHONYL-3-ETHYL-4-(CARBOXYLIC ACID) PYRROLIDIN-2-ONE SOAKED IN PH 9 BUFFER FOR ONE MINUTE
Overview
beta-Lactams inhibit a range of enzymes via acylation of nucleophilic serine residues. Certain gamma-lactam analogues of monocyclic beta-lactams have also been shown to be reversible inhibitors of porcine pancreatic elastase (PPE), forming acyl-enzyme complexes that are stable with respect to hydrolysis. Crystallographic analysis at pH 5 of an acyl-enzyme complex formed with PPE and one of these inhibitors revealed the ester carbonyl located in the oxyanion hole in a similar conformation to that observed in the structure of a complex formed between a heptapeptide (beta-casomorphin-7) and PPE. Only weak electron density was observed for the His-57 side chain in its 'native' conformation. Instead, the His-57 side chain predominantly adopted a conformation rotated approx. 90 degrees from its normal position. PPE-gamma-lactam crystals were subjected to 'pH-jumps' by placing the crystals in a buffer of increased pH prior to freezing for data collection. The results indicate that the conformation of the gamma-lactam-derived acyl-enzyme species in the PPE active site is dependent on pH, a result having implications for the analysis of other serine protease-inhibitor structures at non-catalytic pH values. The results help to define the stereoelectronic relationship between the ester of the acyl-enzyme complex, the side chain of His-57 and the incoming nucleophile during the reversible (de)acylation steps, implying it is closely analogous to the hydrolytic deacylation step during catalytic peptide hydrolysis.
About this Structure
1E34 is a Single protein structure of sequence from Sus scrofa with , and as ligands. Active as Pancreatic elastase, with EC number 3.4.21.36 Known structural/functional Site: . Full crystallographic information is available from OCA.
Reference
'pH-jump' crystallographic analyses of gamma-lactam-porcine pancreatic elastase complexes., Wright PA, Wilmouth RC, Clifton IJ, Schofield CJ, Biochem J. 2000 Oct 15;351 Pt 2:335-40. PMID:11023818
Page seeded by OCA on Thu Feb 21 12:23:15 2008
