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.
[[Image:http://www.google.com/imgres?q=papain+mechanism&um=1&hl=en&client=firefox-a&sa=N&rls=org.mozilla:en-US:official&biw=1439&bih=668&tbm=isch&tbnid=stidXDPH4Sf8ZM:&imgrefurl=http://www.grin.com/en/doc/277519/design-synthesis-and-evaluation-of-cysteine-protease-inhibitors&docid=mam_b12daT8TZM&imgurl=http://www.grin.com/object/external_document.277519/39fb03ee7469e8a03df51acd066b17b2_LARGE.png&w=807&h=851&ei=rhS3Tr-zHeaQ2QWiutGtBA&zoom=1&iact=hc&vpx=1080&vpy=155&dur=19920&hovh=231&hovw=219&tx=146&ty=128&sig=116562181661860499791&page=2&tbnh=132&tbnw=125&start=21&ndsp=24&ved=1t:429,r:6,s:21]]
.
