Sandbox 39
From Proteopedia
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== Function == | == Function == | ||
As a cysteine protease, Papain utilizes a nucleophilic cysteine thiol as part of its catalytic triad. Papain's Cys-25 is deprotonated by its His-159. The now nucleophilic Cys-25 attacks the carbonyl carbon of the peptide backbone, forming an acyl enzyme intermediate in which the peptide's amino terminal is free. Also in this step, His-159 is returned to its deprotonated form. The intermediate is then deacylated by a water molecule, and it releases the carboxyl terminal of the peptide to produce the product and regenerate the active enzyme. This entire mechanism is shown below: | As a cysteine protease, Papain utilizes a nucleophilic cysteine thiol as part of its catalytic triad. Papain's Cys-25 is deprotonated by its His-159. The now nucleophilic Cys-25 attacks the carbonyl carbon of the peptide backbone, forming an acyl enzyme intermediate in which the peptide's amino terminal is free. Also in this step, His-159 is returned to its deprotonated form. The intermediate is then deacylated by a water molecule, and it releases the carboxyl terminal of the peptide to produce the product and regenerate the active enzyme. This entire mechanism is shown below: | ||
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[[Image:jrip.jpg]] | [[Image:jrip.jpg]] | ||
<ref>Image from: | <ref>Image from: | ||
http://upload.wikimedia.org/wikipedia/commons/5/5c/Cysteinprotease_Reaktionsmechanismus.svg</ref>]] | http://upload.wikimedia.org/wikipedia/commons/5/5c/Cysteinprotease_Reaktionsmechanismus.svg</ref>]] | ||
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| + | == Composition and Structure of Papain == | ||
| + | Proteins only consist of certain elements: carbon, hydrogen, nitrogen, oxygen, and sulfur. Enzymes' primary structures allow them to fold optimally and interact with their substrates maximally in order to efficiently catalyze biological reactions. The <scene name='Sandbox_39/Elemental_composition/1'>elemental composition of papain</scene> shows carbon atoms outlined in grey, oxygen atoms in red, nitrogen atoms in blue, and sulfur atoms in yellow. | ||
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<scene name='Sandbox_39/Hydrphobic_residues/1'>hydrophobic residues shown in yellow</scene> | <scene name='Sandbox_39/Hydrphobic_residues/1'>hydrophobic residues shown in yellow</scene> | ||
Revision as of 23:38, 8 November 2011
| Please do NOT make changes to this Sandbox. Sandboxes 30-60 are reserved for use by Biochemistry 410 & 412 at Messiah College taught by Dr. Hannah Tims during Fall 2012 and Spring 2013. |
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Contents |
Papain
Introduction
Papain (9PAP), also known as papaya proteinase I, is an enzyme found in unripe papaya fruit. A cysteine protease, it has been used to break down tough muscle fibers, and hence is often found in powdered meat tenderizers. It is collected from the fruit by scoring its skin and allowing the "sap" to seem out. The sap is then dried and purified.
Function
As a cysteine protease, Papain utilizes a nucleophilic cysteine thiol as part of its catalytic triad. Papain's Cys-25 is deprotonated by its His-159. The now nucleophilic Cys-25 attacks the carbonyl carbon of the peptide backbone, forming an acyl enzyme intermediate in which the peptide's amino terminal is free. Also in this step, His-159 is returned to its deprotonated form. The intermediate is then deacylated by a water molecule, and it releases the carboxyl terminal of the peptide to produce the product and regenerate the active enzyme. This entire mechanism is shown below:
[1]]]
Composition and Structure of Papain
Proteins only consist of certain elements: carbon, hydrogen, nitrogen, oxygen, and sulfur. Enzymes' primary structures allow them to fold optimally and interact with their substrates maximally in order to efficiently catalyze biological reactions. The shows carbon atoms outlined in grey, oxygen atoms in red, nitrogen atoms in blue, and sulfur atoms in yellow.
