Sandbox 32: Difference between revisions
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=='''Catalytic Mechanism'''== | =='''Catalytic Mechanism'''== | ||
[[Image:Papain_Mechanism. | [[Image:Papain_Mechanism.jpg|200px|left|thumb|]] | ||
As a sulfhydryl protease, Papain has a catalytic site with three important residues --Cysteine-25, Histidine-159,and Asparganine176 (4). The catalytic site is located in the <scene name='Sandbox_32/Binding_cleft/2'>binding cleft</scene> between the L and R domains of the protein The <scene name='Sandbox_32/Catalytic_site/1'>catalytic site</scene> centers around Cysteine-25 as it is a sulfhydryl protease. Sulfur on the cysteine will nucelophilically attack its substrate. Histidine acts to deprotonate sulfur (Cys-25), allowing it to be negatively charged. Once sulfur attacks the peptide,the tetrahedral intermediate is stabilized by a proposed oxyanion hole, specifically by asparganine (Asn-176) (1). The charged imidazolium ion of papain will in turn protanate the nitrogen in the peptide bond, releasing the C-terminal part of the peptide (5). Water enters the active site and ultimately regenerates the enzyme and allowing for the release of the N-terminal portion of the cleaved peptide. | As a sulfhydryl protease, Papain has a catalytic site with three important residues --Cysteine-25, Histidine-159,and Asparganine176 (4). The catalytic site is located in the <scene name='Sandbox_32/Binding_cleft/2'>binding cleft</scene> between the L and R domains of the protein The <scene name='Sandbox_32/Catalytic_site/1'>catalytic site</scene> centers around Cysteine-25 as it is a sulfhydryl protease. Sulfur on the cysteine will nucelophilically attack its substrate. Histidine acts to deprotonate sulfur (Cys-25), allowing it to be negatively charged. Once sulfur attacks the peptide,the tetrahedral intermediate is stabilized by a proposed oxyanion hole, specifically by asparganine (Asn-176) (1). The charged imidazolium ion of papain will in turn protanate the nitrogen in the peptide bond, releasing the C-terminal part of the peptide (5). Water enters the active site and ultimately regenerates the enzyme and allowing for the release of the N-terminal portion of the cleaved peptide. | ||
Papain is very non-specific in the type of peptide bonds that it cleaves. It will cleave bonds of most basic amino acids. It will also cleave after leucine or glycine residues and will hydrolyze esters and amides (3). | Papain is very non-specific in the type of peptide bonds that it cleaves. It will cleave bonds of most basic amino acids. It will also cleave after leucine or glycine residues and will hydrolyze esters and amides (3). | ||
=='''Inhibition'''== | =='''Inhibition'''== | ||
