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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History
Papain was originally discovered during the colonial period in Congo. The native inhabitants discovered that wrapping their elephant meat in papaya leaves helped to tenderize the meat. While they did not know the direct cause, this was when the proteolytic enzyme was first discovered. The active binding site of this enzyme was first discovered by Drenth et al., through the crystallographic analysis of the enzymes structure.
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