Sandbox 31: Difference between revisions
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==Introduction== | ==Introduction== | ||
Papain is a cysteine hydrolase (EC 3.4.22.2) that is found naturally occurring in [http://en.wikipedia.org/wiki/Carica_papaya Papaya](''Carica papaya''). Papain is extracted from the latex, leaves and roots of the papaya tree. Papain is a protease commonly used for cell isolation, protein structural studies, cleaving antibodies, and various other research techniques. In addition to use in research, it is commonly used in industry to tenderize meats, remove skin from hides, and clean soft contact lenses. | Papain is a cysteine hydrolase (EC 3.4.22.2) that is found naturally occurring in [http://en.wikipedia.org/wiki/Carica_papaya Papaya](''Carica papaya''). Papain is extracted from the latex, leaves and roots of the papaya tree. Thiol proteases like papain are commonly found in different fruits like pineapples, figs, and kiwis. Papain is a protease commonly used for cell isolation, protein structural studies, cleaving antibodies, and various other research techniques. In addition to use in research, it is commonly used in industry to tenderize meats, remove skin from hides, and clean soft contact lenses. | ||
[[Image:papayas.jpg]] | [[Image:papayas.jpg]] | ||
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[[Image:papain2.jpg]] | [[Image:papain2.jpg]] | ||
This triad interacts with the substrate to catalyze the reaction. The sulfur from CYS 25 attacks the backbone amine on the substrate forming a tetrahedral intermediate. Next, the carbonyl is reformed and the carbon nitrogen bond is broken. A water associated with a nitrogen on HIS 159 then attacks the carbonyl forming a second tetrahedral intermediate. The carbonyl then reforms breaking the carbon-sulfur bond. This leaves a carboxy group on the end of one piece of the substrate and an amino group on the end of the other piece. | This triad interacts with the substrate to catalyze the reaction. The sulfhydryl group on CYS 25 plays the key role in the mechanism, which is why papain is considered a thiol protease. The sulfur from CYS 25 attacks the backbone amine on the substrate forming a tetrahedral intermediate. Next, the carbonyl is reformed and the carbon nitrogen bond is broken. A water associated with a nitrogen on HIS 159 then attacks the carbonyl forming a second tetrahedral intermediate. The carbonyl then reforms breaking the carbon-sulfur bond. This leaves a carboxy group on the end of one piece of the substrate and an amino group on the end of the other piece. | ||
(Mechanism of the Papain Enzyme with substrate) | (Mechanism of the Papain Enzyme with substrate) | ||
