Aspartate

Aspartic proteases/acidic proteases are the endopeptidases which requires aspartic acid residues for their catalysis and usually function in acid solutions. Due to their functioning in acid environment the functioning of aspartic proteases are limited to certain locations. The catalytic site consists of two aspartic acid residues at positions 32 and 215. Two aspartic residues which mediate the nucleophilic attack on the peptide bond by activating the water molecule (James, 2004). Aspartic proteases exhibit maximal activity at 3 to 4, an isoelectric point in the range of pH 3 to 4.5 and molecular masses are in the range of 30 to 45 kDa (Rao et al., 1998). The active-site aspartic acid residue is situated within the motif Asp-Xaa-Gly, in which Xaa can be Ser or Thr. The aspartic proteases are inhibited by pepstatin, along with being sensitive to diazoketone compounds such as diazoacetyl-DL-norleucine methyl ester (DAN) and 1,2-epoxy-3-(p-nitrophenoxy)propane (EPNP) in the presence of copper ions (Rao et al., 1998).