Papain: Difference between revisions

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<scene name='Sandbox_31/Leupeptin/1'>Leupeptin</scene> is a commonly studied inhibitor of proteases (seen in the Jmol as ball and stick model).  It inhibits by binding and interacting with the active site which allows it to block the enzyme's desired protein substrate.  There are many <scene name='Sandbox_31/1popligand_contacts/1'>Residues</scene> that interact with Leupeptin in the active site.  The predominant interaction is from hydrophobic interactions between Leupeptin and <scene name='Sandbox_31/1pophydrointeract/1'>active site residues</scene>.  In addition to hydrophobic interactions, there are also some hydrogen bonding interactions to hold Leupeptin in the active site of papain.  Leupeptin works well at blocking papain from its enzymatic duties.  A recent study has shown that Leupeptin actually forms a covalent bond between its <scene name='Sandbox_31/Leupeptin_active/1'>Carbonyl Carbon</scene> and CYS 25.  In addition, the residues Gln 19 and CYS 25 form <scene name='Sandbox_31/Leupeptin_active/2'>hydrogen bonds</scene> with the Leupeptin molecule

Cathepsin L is another inhibitor of the papain enzyme.  Cathepsin L interacts with the <scene name='Sandbox_31/Cathepl/1'>papain residues</scene> Gln19, Cys25, Gly66, Asp158, and Trp177 by hydrogen bonding them (Cathepsin L is lime green in the model, and the papain residues active in hydrogen bonding with Cathepsin L are highlighted with yellow halos). In addition to hydrogen bonding, hydrophobic interactions exist to exclude water, allowing the papain enzyme and Cathepsin L to associate even closer.  Finally, <scene name='Sandbox_31/Stacking/1'>Ring Stacking</scene> between Trp177 and the Capthespin L molecule hold them tightly together.<ref>http://pubs.acs.org/doi/abs/10.1021/ci800085c</ref> Cathepsin L plays a roll in many different diseases including malaria, leishmaniasis, Chagas' disease, African trypanosomiasis, toxoplasmosis, and amoebiasis.<ref>http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2923042/?tool=pubmed</ref>Some studies show that there is a relation between cathepsins and certain cancers, alzheimer's, and arthritis.<ref>http://www.biomedcentral.com/1472-6807/10/30</ref>  

<scene name='Sandbox_36/Papain_inhibitor_space_fill/1'>Stefin B</scene> acts as a competitive inhibitor to cysteine proteases-- it binds tightly but reversibly to the papain active site.  Stefin inhibitors are characterized by M_r of about 11,000, no disulfide bonds and no associated carbohydrates.