Sandbox Reserved 773: Difference between revisions
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== Cofactor and Substrate Binding Pocket == | == Cofactor and Substrate Binding Pocket == | ||
[[Image:Histidine Decarboxylase Binding Site.png|thumb|Figure 4. Interactions between enzyme HDC and cofactor-substrate PLP-HME at the binding site <ref name= | [[Image:Histidine Decarboxylase Binding Site.png|thumb|Figure 4. Interactions between enzyme HDC and cofactor-substrate PLP-HME at the binding site <ref name=jbc/>.]] | ||
The binding pocket for the cofactor PLP and the substrate histidine is located at the large domain. Since Histidine methyl ester (HME) is a substrate analog, PLP-HME can be utilized to demonstrate the binding interaction for the substrate-enzyme transition state at the active site <ref name=jbc/> <ref name=inhibition>PMID:850236</ref>. A one-dimensional representation of PLP-HME residing in the binding pocket can be seen in Figure 3. The hydrophobic pocket of the active site are produced by several hydrophobic amino acids including Trp-72, Tyr-80, Leu-102, Phe-104, Ala-275, Tyr-334, Ile-436 (Figure 3). This hydrophobic pocket allow for the substrate to be protected from the solvent during the catalytic reaction. | The binding pocket for the cofactor PLP and the substrate histidine is located at the large domain. Since Histidine methyl ester (HME) is a substrate analog, PLP-HME can be utilized to demonstrate the binding interaction for the substrate-enzyme transition state at the active site <ref name=jbc/> <ref name=inhibition>PMID:850236</ref>. A one-dimensional representation of PLP-HME residing in the binding pocket can be seen in Figure 3. The hydrophobic pocket of the active site are produced by several hydrophobic amino acids including Trp-72, Tyr-80, Leu-102, Phe-104, Ala-275, Tyr-334, Ile-436 (Figure 3). This hydrophobic pocket allow for the substrate to be protected from the solvent during the catalytic reaction. | ||
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== Enzymatic Mechanism == | == Enzymatic Mechanism == | ||
During the catalytic reaction by HDC, the carboxyl group of L-histamine is removed with the help of cofactor pyridoxal-5'-phosphate (PLP) to generate the product histamine and byproduct carbon dioxide (CO2). The overall catalytic reaction is proposed to be a 1-step mechanism shown below <ref name= | During the catalytic reaction by HDC, the carboxyl group of L-histamine is removed with the help of cofactor pyridoxal-5'-phosphate (PLP) to generate the product histamine and byproduct carbon dioxide (CO2). The overall catalytic reaction is proposed to be a 1-step mechanism shown below <ref name=metabolism/>: | ||
[[Image:Histidine decarboxylase mechanism.svg.png|center]] | [[Image:Histidine decarboxylase mechanism.svg.png|center]] | ||
