Papain: Difference between revisions

'''Papain'''. Meat tenderizer. Old time home remedy for insect, jellyfish, and stingray stings<ref>[http://www.ameriden.com/products/advanced-digestive-enzyme/] Ameridan International</ref>. Who would have thought that a sulfhydryl protease from the latex of the papaya fruit, ''Carica papaya'' and ''Vasconcellea cundinamarcensis'', would have such a practical application beyond Proteopedia?

Papain's enzymatic use was first discovered in 1873 by G.C. Roy who published his results in the Calcutta Medical Journal in the article, "The Solvent Action of Papaya Juice on Nitrogenous Articles of Food." In 1879, Papain was named officially by Wurtz and Bouchut, who managed to partially purify the product from the sap of papaya. It wasn't until the mid-twentieth century that the complete purification and isolation of Papain was achieved. In 1968, Drenth et al. determined the structure of Papain by [[X-ray crystallography|x-ray crystallography]], making it the second enzyme whose structure was successfully determined by x-ray crystallography. Additionally, Papain was the first cysteine protease to have its structure identified.<ref name="Worthington" /> In 1984, Kamphuis et al. determined the geometry of the active site, and the three-dimensional structure was visualized to a 1.65 Angstrom solution.<ref name="Structure">PMID:6502713</ref> Today, studies continue on the stability of Papain, involving changes in environmental conditions as well as testing of inhibitors such as phenylmethanesulfonylfluoride (PMSF), TLCK, TPCK, aplh2-macroglobulin, heavy metals, AEBSF, antipain, cystatin, E-64, leupeptin, sulfhydryl binding agents, carbonyl reagents, and alkylating agents.<ref name="Worthington" />

==Structure==

There are a small number of <scene name='Papain/Stefin_b_hbonds/2'>direct hydrogen bonds</scene> (labeled in <scene name='Papain/Stefin_b_hbonds/1'>this scene</scene>, between Stefin B and Papain, however there are many more polar interactions mediated by <scene name='Papain/Stfn_b_solvent_intrxns/1'>solvent bridges</scene>, the solvent being mainly <big><b><font color='darkturquoise'>water</font></b></big>.  Thirteen solvent molecules of water bridge polar residues of the enzyme and inhibitor.  Seventeen hydrogen bonds are made with a solvent molecule and Stefin B.  Fourteen of these bridges form a Papain contact.  The rest of the interactions are largely hydrophobic-- involving apolar <scene name='Papain/Stefin_b_vdw/2'>Van der Waals forces</scene>.<ref> PMID:2347312 </ref>

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==References==  

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