Catalytic residues are highly conserved among the proteins, amino acid residues which are sequentially neighbor to the catalytic sites, some extent contain similar structural information. Collected data from the Protein Data Bank (PDB) database contain one aspartic protease group (n=28) and two serine protease groups (n=37 and n=7) specified by catalytic triads. Analysis of the molecular structures of amino acids by Sparse Linear Discriminant Analysis (SLDA) and t-test revealed that the neighbor residues contain information on the functional differentiation of the enzymes, suggesting that the sequentially close residues to the catalytic triads are more preserved than the rest of amino acid residues. Moreover, similar structural properties in the vicinity of all three catalytic sites can be observed by correlation heat maps. These results can hopefully facilitate a better understanding of the protein function from structure and lead to novel protein design.