Nature of the inactivation of elastase by N-peptidyl-O-aroyl hydroxylamine as a function of pH.
The mechanism of inactivation of porcine pancreatic elastase (PPE) by N-peptidyl-O-aroylhydroxylamine was studied by X-ray crystallography. The inactivator forms a stable complex with the enzyme by means of a covalent attachment to the active site Ser 203(195) O gamma. The nature of the complex is, however, different depending on the pH at which the inactivation reaction occurs. At pH 5, the complex formed is a hydroxylamine derivative of Ser 203(195) in which the O gamma of serine is the oxygen of the hydroxylamine derivative. At pH 7.5, the complex formed is a carbamate derivative at Ser 203(195) O gamma. In both types of complexes, the inactivator binds in the S' subsites of the enzyme instead of forming the usual antiparallel beta-sheet with the S subsites. The implication for the mechanism of inactivation at different pHs is discussed.
Ding
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Department of Chemistry, Brandeis University, Waltham, Massachusetts 02254, USA.
Rasmussen
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Demuth
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Ringe
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Steinmetz
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D000818:Animals; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004151:Dipeptides / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D006898:Hydroxylamines / Q000494:pharmacology*; D008958:Models, Molecular; D010196:Pancreatic Elastase / Q000037:antagonists & inhibitors*; D017433:Protein Structure, Secondary; D012694:Serine / Q000737:chemistry; D015842:Serine Proteinase Inhibitors; D013552:Swine
D004151:Dipeptides; D006898:Hydroxylamines; C094179:N-(tert-butoxycarbonylalanylalanyl)-O-(4-nitrobenzoyl)hydroxylamine; D015842:Serine Proteinase Inhibitors; D012694:Serine; D010196:Pancreatic Elastase