DOPA decarboxylase: Difference between revisions

Line 55:

[[image:untitled.png|thumb|center|400px|]]

===~~Critical Residues~~===

===Mechanism Breakdown===

====~~Lys303~~====

====Step 1: Formation of an Internal Aldimine====

====~~Asp271~~====

The first step of the reaction involves the binding of PLP to the enzyme via a Schiff base linkage between the aldehyde group of PLP and the ε—amino group of Lys303. An extensive hydrogen bond network further anchors PLP to the enzyme.

====~~His192~~====

====Step 2: Formation of an External Aldimine====

====~~Arg355=~~===

The second step of the reaction involves the binding of PLP with the substrate via a Schiff base linkage. The imine formed in the first step of the reaction is more succeptible than a free aldehyde to nucleophilic attack by the amino group of the substrate. Thus, not only does the internal aldimine between PLP and the Lys303 bind cofactor, it also serves to facilitate chemistry occurring in this second step.

====~~Tyr332~~====

====Step 3: Formation of a Quinonoid Intermediate====

The formation of the quinonoid intermediate is common to all PLP-dependent enzymes, yet the orientation of the intermediate, as determined by key residues of the enzyme active site, determines the subsequent reaction (for example whether it will be a decarboxylation or transamination). A salt bridge that exists between Asp271 and the protonated pyridine nitrogen of PLP further enhances the ability of PLP to act as an electron sink and promote catalysis. As well, During the formation of the quinonoid intermediate, carbon dioxide is released.

====Step 4: Formation of an External Aldimine===

The formation of the external aldimine between the product and PLP is the fourth step of the reaction. Here, Tyr332, with the assistance of His192, likely donates a proton to the quinonoid Cα intermediate.

====Step 5: Formation of an Internal Aldimine and Product Release====

Formation of an internal aldimine between PLP and Lys303 regenerates the enzyme. It has been shown that Lys303 plays a role in product release by presumably displacing the amino group of the product by nucleophilic attack of the imine bond of the external aldimine.

==Classification==

DOPA decarboxylase: Difference between revisions

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@@ Line 55: / Line 55: @@
 [[image:untitled.png|thumb|center|400px|]]
-===Critical Residues===
+===Mechanism Breakdown===
-====Lys303====
+====Step 1: Formation of an Internal Aldimine====
-====Asp271====
+The first step of the reaction involves the binding of PLP to the enzyme via a Schiff base linkage between the aldehyde group of PLP and the ε—amino group of Lys303. An extensive hydrogen bond network further anchors PLP to the enzyme.
-====His192====
+====Step 2: Formation of an External Aldimine====
-====Arg355====
+The second step of the reaction involves the binding of PLP with the substrate via a Schiff base linkage. The imine formed in the first step of the reaction is more succeptible  than a free aldehyde to nucleophilic attack by the amino group of the substrate. Thus, not only does the internal aldimine between PLP and the Lys303 bind cofactor, it also serves to facilitate chemistry occurring in this second step.
-====Tyr332====
+====Step 3: Formation of a Quinonoid Intermediate====
+The formation of the quinonoid intermediate is common to all PLP-dependent enzymes, yet the orientation of the intermediate, as determined by key residues of the enzyme active site, determines the subsequent reaction (for example whether it will be a decarboxylation or transamination). A salt bridge that exists between Asp271 and the protonated pyridine nitrogen of PLP further enhances the ability of PLP to act as an electron sink and promote catalysis. As well, During the formation of the quinonoid intermediate, carbon dioxide is released.
+ ====Step 4: Formation of an External Aldimine===
+The formation of the external aldimine between the product and PLP is the fourth step of the reaction. Here, Tyr332, with the assistance of His192, likely donates a proton to the quinonoid Cα intermediate.
+====Step 5: Formation of an Internal Aldimine and Product Release====
+Formation of an internal aldimine between PLP and Lys303 regenerates the enzyme. It has been shown that Lys303 plays a role in product release by presumably displacing the amino group of the product by nucleophilic attack of the imine bond of the external aldimine.
 ==Classification==