Sandbox Reserved 1051: Difference between revisions

[[Image:AG85C homodimer.jpg |100 xp|left|thumb|'''Figure 1.'''  Ag85C homodimer. ]]  

[[Image:Ag85C active site 2.jpg |100 xp|left|thumb|'''Figure 2.'''Ag85C with labeled active site residues. The three catalytic residues, Ser124, Glu228, and His260, as well as Cys209 are labeled.]] Within the <scene name='69/697503/Active_site/2'>Ag85C active site</scene>, three residues function together to make up the <scene name='69/694218/Catalytic_triad/2'>catalytic triad</scene> for this enzyme (Figure 2).  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 [http://en.wikipedia.org/wiki/Chymotrypsin chymotrypsin mechanism]. 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 α-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.<ref name="Favrot"/>