Introduction:
Papain is a protease derived from the latex of the papaya fruit. The molecule consists of 212 amino acid residues that contribute to a single polypeptide chain. The secondary structure of this molecule consists of 25%. and 21% . Traditionally, Papain has be used as a commercial meat tenderizer. This enzyme also has some medicinal uses, as it has be been used in wound debridement, and is ocassionally administered as a dietary supplement. This enzyme is able to aid in digestive problems, as it is able to break down food so it is easier to digest.
Function:
This hydrolytic enzyme is able to break peptide bonds through the deprotonation of Cys-25 by His-159, with the help of Asparagine-125, which stabilizes the Histadine ring in order for this deprotonation to take place. The Cys-25 residue is then able to perform a nucleophilic attack on the carbonyl carbon of the peptide backbone, freeing the amino terminal of the peptide, forming a covalent intermediate. Next, the enzyme is deacylated by water, and the carboxy-terminal portion of the peptide is released.
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