Sandbox Reserved 1051: Difference between revisions
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===Active Site=== | ===Active Site=== | ||
Within the active site | Within the <scene name='69/697503/Active_site/2'>Ag85C active site</scene>, three residues function together to make up the catalytic triad for this enzyme. The goal of the catalytic triad is to generate a nucleophilic residue for covalent catalysis by using an acid-base-nucleophile triad. These three residues, Ser124, Glu228, and His260 form a charge-relay network to polarize and activate the nucleophile, Ser124, which is then able to attack the substrate to form a covalent intermediate, which is then hydrolysed to regenerate a free enzyme. This charge relay is an example of the well known chymotrypsin mechanism [[http://en.wikipedia.org/wiki/Chymotrypsin]]. Overall, it is suggested that increased enzymatic activity is attributed to the components of the active site remaining intact so that the serine nucleophile can react to form an intermediary and stabilize the transition state formed during catalysis. | ||
In the native structure, the alpha-helix 9 maintains a kinked conformation necessary for correct formation of the hydrogen bonding network between the residues of the catalytic triad, thus allowing for high enzymatic activity (Favrot). | In the native structure, the alpha-helix 9 maintains a kinked conformation necessary for correct formation of the hydrogen bonding network between the residues of the catalytic triad, thus allowing for high enzymatic activity (Favrot). | ||
<scene name='69/697503/Active_site/2'>ag85C active site</scene> | |||
===Cystine 209=== | ===Cystine 209=== | ||
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===Ag85C-H260Q=== | ===Ag85C-H260Q=== | ||
In this mutant of Ag85C, a shift in helix alpha-9 prevents the formation of any stabilizing hydrogen bonds between residues His 260 and Glu 228, thus decreasing its enzymatic activity. The conversion of the glutamate, a key player in the catalytic triad, to the corresponding amide-containing side chain as well as a loss of a general base in the charge relay are both key causes for the loss of function. | In this mutant of Ag85C, a shift in helix alpha-9 prevents the formation of any stabilizing hydrogen bonds between residues His 260 and Glu 228, thus decreasing its enzymatic activity. The conversion of the glutamate, a key player in the catalytic triad, to the corresponding amide-containing side chain as well as a loss of a general base in the charge relay are both key causes for the loss of function. | ||
