Sandbox 31: Difference between revisions
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(Active Site of Papain) | (Active Site of Papain) | ||
[[Image:papain2.jpg]] | [[Image:papain2.jpg|150px|left|thumb|]] | ||
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. | 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. | ||
