Multiple choice

Choose the correct enzyme(s) from the following which belong to serine proteases.

  1. Subtilisin

  2. Trypsin

  3. Elastase

  4. Chymotrypsin

  5. All of the above
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E Correct answer
Explanation

Subtilisin, a serine protease, is present in prokaryotes. Subtilisin uses a catalytic triad for creating a nucleophilic serine. Trypsins are proteases which cleave peptide bonds after arginine or lysine and this particularity is guided by the residue present at the bottom of the S1 pocket of the enzyme. Elastase proteases have a smaller S1 aperture than chymotrypsin and trypsin proteases. Therefore, residues like glycine, valine and alanine are preferred. Chymotrypsin proteases have more hydrophobic S1 pocket than trypsin proteases. Therefore, medium and large hydrophobic residues like phenylalanine, tryptophan and tyrosine are preferred. Thus, all the enzymes belong to the category of serine proteases.

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