Journal:Acta Cryst F:S2053230X20002988
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This enzyme was originally named AGXT2L1 (AGXT2-like 1) based on its homology to alanine glyoxylate aminotransferase 2 (AGXT2), a mitochondrial PLP-dependent enzyme that transaminates a variety of substrates while also acting as a lyase on L-cysteine conjugates. Unlike AGXT2, however, hEtnppl is almost completely inactive as a transaminase. Instead, it was shown to catalyze the irreversible 1,2-elimination of O-phosphophenanolamine (PEA) to produce acetaldehyde, phosphate and ammonia. | This enzyme was originally named AGXT2L1 (AGXT2-like 1) based on its homology to alanine glyoxylate aminotransferase 2 (AGXT2), a mitochondrial PLP-dependent enzyme that transaminates a variety of substrates while also acting as a lyase on L-cysteine conjugates. Unlike AGXT2, however, hEtnppl is almost completely inactive as a transaminase. Instead, it was shown to catalyze the irreversible 1,2-elimination of O-phosphophenanolamine (PEA) to produce acetaldehyde, phosphate and ammonia. | ||
| - | Overall structure of the PMP-bound form of hEtnppl: | + | Overall structure of the PMP-bound form of hEtnppl (PDB entry [[6tor]]): |
*<scene name='83/837886/Cv/2'>First view</scene>. Chains A, and B are colored in blue and cyan, respectively. The bound PMP molecule is represented as grey stick. | *<scene name='83/837886/Cv/2'>First view</scene>. Chains A, and B are colored in blue and cyan, respectively. The bound PMP molecule is represented as grey stick. | ||
| - | *<scene name='83/837886/Cv/3'>Second view after 90° rotation</scene>. | + | *Although you may explore and rotate every structure with the mouse, here you can see a <scene name='83/837886/Cv/3'>Second view after 90° rotation</scene>. |
<scene name='83/837886/Cv/4'>Structure of the chain A</scene>. The N-terminal lobe (residues 1-85), large domain (residues 86-301) and C-terminal lobe (residues 302-499) are colored in cyan, magenta and green, respectively. | <scene name='83/837886/Cv/4'>Structure of the chain A</scene>. The N-terminal lobe (residues 1-85), large domain (residues 86-301) and C-terminal lobe (residues 302-499) are colored in cyan, magenta and green, respectively. | ||
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Dimer interface in the hEtnppl structure (spacefill representation of the dimer subunits): | Dimer interface in the hEtnppl structure (spacefill representation of the dimer subunits): | ||
*<scene name='83/837886/Cv/17'>First view</scene>. The critically important residues forming interface contacts are colored in blue (chain A) and cyan (chain B). | *<scene name='83/837886/Cv/17'>First view</scene>. The critically important residues forming interface contacts are colored in blue (chain A) and cyan (chain B). | ||
| - | *<scene name='83/837886/Cv/18'>Second view after 90° rotation</scene>. | + | *Although you may explore and rotate every structure with the mouse, here you can see a <scene name='83/837886/Cv/18'>Second view after 90° rotation</scene>. |
<scene name='83/837886/Cv/20'>The critically important residues forming interface contacts</scene> are labeled. Hydrogen bonds are indicated by dashed lines. | <scene name='83/837886/Cv/20'>The critically important residues forming interface contacts</scene> are labeled. Hydrogen bonds are indicated by dashed lines. | ||
The crystal structure of hEtnppl (determined at 2.05 Å resolution) shows high similarity to the crystal structure of the phospho-lyase A1RDF1 from ''Arthrobacter aurescens'' TC1, which so far has been the only phospho-lyase structure reported in the literature. The active site of hEtnppl is located at the interface between the two subunits of the dimer, each subunit making crucial contributions to the active site. Most of the residues that line the catalytic pocket correspond to those found in the close structural homolog A1RDF1, strongly suggesting that these enzymes share a common mechanism. While confirming the presence of a cluster of positively charged residues for the recognition of the phosphate moiety of the substrate, the structure of the active site of hEtnppl suggests a striking mobility of the crucial catalytic residue K278. In hEtnppl, the cofactor binds essentially in the same position as in A1RDF1 in complex with <scene name='83/837886/Cv/24'>PLP (internal aldimine)</scene> and <scene name='83/837886/Cv/26'>PLP-PEA (external aldimine)</scene> [key residues of hEtnppl (green) and A1RDF1 (white) active site, and molecule bound are presented in ball-and-sticks, and are numbered in the corresponding color. Residue from the opposite monomer are marked (*). Water molecules are shown as red spheres]. However, in the crystal structure of hEtnppl, the cofactor does not covalently bind the ε-amino group of the adjacent K278 residue, suggesting that the cofactor captured in this structure is not PLP but PMP (pyridoxamine-5'-phosphate), an intermediate in transamination reactions. | The crystal structure of hEtnppl (determined at 2.05 Å resolution) shows high similarity to the crystal structure of the phospho-lyase A1RDF1 from ''Arthrobacter aurescens'' TC1, which so far has been the only phospho-lyase structure reported in the literature. The active site of hEtnppl is located at the interface between the two subunits of the dimer, each subunit making crucial contributions to the active site. Most of the residues that line the catalytic pocket correspond to those found in the close structural homolog A1RDF1, strongly suggesting that these enzymes share a common mechanism. While confirming the presence of a cluster of positively charged residues for the recognition of the phosphate moiety of the substrate, the structure of the active site of hEtnppl suggests a striking mobility of the crucial catalytic residue K278. In hEtnppl, the cofactor binds essentially in the same position as in A1RDF1 in complex with <scene name='83/837886/Cv/24'>PLP (internal aldimine)</scene> and <scene name='83/837886/Cv/26'>PLP-PEA (external aldimine)</scene> [key residues of hEtnppl (green) and A1RDF1 (white) active site, and molecule bound are presented in ball-and-sticks, and are numbered in the corresponding color. Residue from the opposite monomer are marked (*). Water molecules are shown as red spheres]. However, in the crystal structure of hEtnppl, the cofactor does not covalently bind the ε-amino group of the adjacent K278 residue, suggesting that the cofactor captured in this structure is not PLP but PMP (pyridoxamine-5'-phosphate), an intermediate in transamination reactions. | ||
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| + | '''PDB reference:''' human ''O''-phosphoethanolamine phospho-lyase, [[6tor]]. | ||
<b>References</b><br> | <b>References</b><br> | ||
Current revision
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