User:Alexander Rudecki/Sandbox 1: Difference between revisions

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===Protein Family===

DromeQC belongs to the α/β-hydrolase fold superfamily; this superfamily exhibits a β-sheet core (5-8 strands) connected to α helices forming an α/β/α sandwhich<ref name=“family”>PMID: 23193256</ref>. As of present, the ESTHER database (ESTerases and α/β-Hydrolase Enzymes and Relatives) contains 168 protein families<ref>Lenfant, N., Hotelier, T., Velluet, E., Bourne, Y., Marchot, P., and A Chatonnet. (2013) ESTHER, the database of the alpha/beta-hydrolase fold superfamily of proteins: tools to explore diversity of functions. Nucleic Acids Research 41: D423-9. [http://bioweb.ensam.inra.fr/ESTHER/general?what=index]</ref>. Most of the proteins in this superfamily function via a conserved catalytic triad - a nucleophile, acid and base - with the residues present on the loops of the active site<ref name=“family”/>. Further information of this is found in the section #REDIRECT [[Alexander Rudecki/Sandbox 1#Catalytic Mechanism]].

It is interesting that DromeQC prevents protein degradation from aminopeptidases, yet theses two enzymes share a common fold and active site residues<ref>PMID: 15028118</ref>. This suggests that the enzymes act in a similar manner, with contrasting effects on substrate.

===Location===

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===Catalytic Mechanism===

DromeQC is the enzyme responsible for this post-translational processing of polypeptides. DromeQC catalyzes the cyclization of N-terminal glutamine, and to a lesser extent glutamate, into pyroglutamic acid (5-oxo-L-proline, or <Glu) (Figure 4). ~~Cyclization~~ occurs via a nucleophilic attack of the α-amine on the γ carbon in the glutamine side chain. The enzymatic mechanism for DromeQC is still undetermined, but it seems plausible that it follows that of its human orthologue. In hQC, the N-terminus of the peptide substrate is inserted into the active site pocket, where the γ amide oxygen chelates the catalytic zinc ion<ref name="mechanism">PMID: 18470930</ref>. This ion-dipole interaction causes carbonyl polarization, making it a better electrophile. To facilitate the reaction, a conserved glutamate (Glu201) acts as both a general base and acid. Glu201 abstracts a proton from the α-amino group, causing it to nucleophilically attack the γ amide oxygen. This produces a tetrahedral intermediate with a charged oxygen that is stabilized by Zn<sup>2+</sup>. Glu201 then protonates the γ amide nitrogen, and an amine group is expelled as the carbonyl reforms. Also essential to this mechanism is a conserved aspartate (Asp248) that coordinates/stabilizes the leaving amine group.

DromeQC is the enzyme responsible for this post-translational processing of polypeptides. DromeQC catalyzes the cyclization of N-terminal glutamine, and to a lesser extent glutamate, into pyroglutamic acid (5-oxo-L-proline, or <Glu) (Figure 4). This enzyme can be categorized as follows:

:-transferase (2)

::-acyltransferase (2.3)

::-aminoacyltransferase (2.3.2)

::-acts on glutaminyl/glutamyl residues (2.3.2.5)

The cyclization reaction occurs via a nucleophilic attack of the α-amine on the γ carbon in the glutamine side chain. The enzymatic mechanism for DromeQC is still undetermined, but it seems plausible that it follows that of its human orthologue. In hQC, the N-terminus of the peptide substrate is inserted into the active site pocket, where the γ amide oxygen chelates the catalytic zinc ion<ref name="mechanism">PMID: 18470930</ref>. This ion-dipole interaction causes carbonyl polarization, making it a better electrophile. To facilitate the reaction, a conserved glutamate (Glu201) acts as both a general base and acid. Glu201 abstracts a proton from the α-amino group, causing it to nucleophilically attack the γ amide oxygen. This produces a tetrahedral intermediate with a charged oxygen that is stabilized by Zn<sup>2+</sup>. Glu201 then protonates the γ amide nitrogen, and an amine group is expelled as the carbonyl reforms. Also essential to this mechanism is a conserved aspartate (Asp248) that coordinates/stabilizes the leaving amine group.

@@ Line 8: / Line 8: @@
 ===Protein Family===
+DromeQC belongs to the α/β-hydrolase fold superfamily; this superfamily exhibits a β-sheet core (5-8 strands) connected to α helices forming an α/β/α sandwhich<ref name=“family”>PMID: 23193256</ref>. As of present, the ESTHER database (ESTerases and α/β-Hydrolase Enzymes and Relatives) contains 168 protein families<ref>Lenfant, N., Hotelier, T., Velluet, E., Bourne, Y., Marchot, P., and A Chatonnet. (2013) ESTHER, the database of the alpha/beta-hydrolase fold superfamily of proteins: tools to explore diversity of functions. Nucleic Acids Research 41: D423-9. [http://bioweb.ensam.inra.fr/ESTHER/general?what=index]</ref>. Most of the proteins in this superfamily function via a conserved catalytic triad - a nucleophile, acid and base - with the residues present on the loops of the active site<ref name=“family”/>. Further information of this is found in the section #REDIRECT [[Alexander Rudecki/Sandbox 1#Catalytic Mechanism]].
+It is interesting that DromeQC prevents protein degradation from aminopeptidases, yet theses two enzymes share a common fold and active site residues<ref>PMID: 15028118</ref>. This suggests that the enzymes act in a similar manner, with contrasting effects on substrate.
 ===Location===
@@ Line 46: / Line 50: @@
 ===Catalytic Mechanism===
-DromeQC is the enzyme responsible for this post-translational processing of polypeptides. DromeQC catalyzes the cyclization of N-terminal glutamine, and to a lesser extent glutamate, into pyroglutamic acid (5-oxo-L-proline, or <Glu) (Figure 4). Cyclization occurs via a nucleophilic attack of the α-amine on the γ carbon in the glutamine side chain. The enzymatic mechanism for DromeQC is still undetermined, but it seems plausible that it follows that of its human orthologue. In hQC, the N-terminus of the peptide substrate is inserted into the active site pocket, where the γ amide oxygen chelates the catalytic zinc ion<ref name="mechanism">PMID: 18470930</ref>. This ion-dipole interaction causes carbonyl polarization, making it a better electrophile. To facilitate the reaction, a conserved glutamate (Glu201) acts as both a general base and acid. Glu201 abstracts a proton from the α-amino group, causing it to nucleophilically attack the γ amide oxygen. This produces a tetrahedral intermediate with a charged oxygen that is stabilized by Zn<sup>2+</sup>. Glu201 then protonates the γ amide nitrogen, and an amine group is expelled as the carbonyl reforms. Also essential to this mechanism is a conserved aspartate (Asp248) that coordinates/stabilizes the leaving amine group.
+DromeQC is the enzyme responsible for this post-translational processing of polypeptides. DromeQC catalyzes the cyclization of N-terminal glutamine, and to a lesser extent glutamate, into pyroglutamic acid (5-oxo-L-proline, or <Glu) (Figure 4). This enzyme can be categorized as follows:
+:-transferase (2)
+::-acyltransferase (2.3)
+::-aminoacyltransferase (2.3.2)
+::-acts on glutaminyl/glutamyl residues (2.3.2.5)
+The cyclization reaction occurs via a nucleophilic attack of the α-amine on the γ carbon in the glutamine side chain. The enzymatic mechanism for DromeQC is still undetermined, but it seems plausible that it follows that of its human orthologue. In hQC, the N-terminus of the peptide substrate is inserted into the active site pocket, where the γ amide oxygen chelates the catalytic zinc ion<ref name="mechanism">PMID: 18470930</ref>. This ion-dipole interaction causes carbonyl polarization, making it a better electrophile. To facilitate the reaction, a conserved glutamate (Glu201) acts as both a general base and acid. Glu201 abstracts a proton from the α-amino group, causing it to nucleophilically attack the γ amide oxygen. This produces a tetrahedral intermediate with a charged oxygen that is stabilized by Zn<sup>2+</sup>. Glu201 then protonates the γ amide nitrogen, and an amine group is expelled as the carbonyl reforms. Also essential to this mechanism is a conserved aspartate (Asp248) that coordinates/stabilizes the leaving amine group.