While a number of different mechanisms for aspartyl proteases have been proposed, the most widely accepted is a general acid-base mechanism involving coordination of a water molecule between the two highly conserved aspartate residues.[6][7] One aspartate activates the water by abstracting a proton, enabling the water to perform a nucleophilic attack on the carbonyl carbon of the substrate scissile bond, generating a tetrahedral oxyanion intermediate stabilized by hydrogen-bonding with the second aspartic acid. Rearrangement of this intermediate leads to protonation of the scissile amide which results in the splitting of the substrate peptide into two product peptides.