Quantum-Chemical Study of the Catalytic Mechanism of Aspartic Proteinases
Aspartic proteinases are a group of enzymes functioning by a general base mechanism, the water molecule serving as nucleophile.1 The X-ray data (for example references 2-4) clearly show that two aspartic acid residues Asp32 and Asp215 (porcine pepsin sequence) are involved in catalysis. These residues are bound to each other by a hydrogen bond and possess different acid dissociation constants.(pKa) (for porcine pepsin, 1.5 and 4.7, respectively.5 The hypothesis on the action mechanism of aspartic proteinases has been put forward6 which is compatible with most of the available data. The aim of this report is to check the validity of this mechanism by quantum-chemical analysis.
KeywordsActivation Barrier Bond Order Aspartic Proteinase Aspartic Acid Residue Acid Dissociation Constant
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