Aconitase

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'''Aconitase (ACO)''' is an enzymatic domain that confers the ability to catalyse the equilibrium
'''Aconitase (ACO)''' is an enzymatic domain that confers the ability to catalyse the equilibrium
-
:citrate = aconitate + H<sub>2</sub>O = isocitrate
+
:citrate = aconitate + H<sub>2</sub>O = L-isocitrate
This reaction is part of the citrate (TCA-, Krebs-)cycle.
This reaction is part of the citrate (TCA-, Krebs-)cycle.
In most organims, there is a cytosolic enzyme with an ACO domain (cAc), and in eukaryotes, a second copy of it was introduced with mitochondria (mAc). Plants developed even more copies in mitochondria.
In most organims, there is a cytosolic enzyme with an ACO domain (cAc), and in eukaryotes, a second copy of it was introduced with mitochondria (mAc). Plants developed even more copies in mitochondria.
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<applet load='Morph_2ipy-2b3x.pdb.gz' scene='Aconitase/2ipy-total/2' size='400' frame='true' align='right' caption="" />A specialty of cAc is that in mammals it has developed a <scene name='Aconitase/2ipy-total/2'>second function</scene> as inhibitor of <scene name='Aconitase/2ipy-rna/1'>those mRNA</scene> that carry an <scene name='Aconitase/2ipy-rna-ire/1'>iron-regulatory element (IRE)</scene>. Therefore, the cytosolic cAc is named IREBP for IRE-binding protein when this function is talked about. Only one of the two functions is active, depending on whether <scene name='Aconitase/2b3x-cluster/1'>the (4Fe4S) cofactor</scene> is present in the molecule: it's essential for <scene name='Aconitase/2b3x-total/1'>the ACO function</scene>. You can see, by <scene name='Aconitase/Morph/2'>looking at the morph</scene>, how much the enzyme structure differs between those two functions.
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== Catalytic mechanism of mitochondrial ACO ==
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<applet load=7acn scene='Aconitase/7acn-sf4/1' size='400' frame='true' align='left' caption="Mitochondrial aconitase from pig, PDB [[7acn]]." />The bulk of citrate cycle processing happens in mitochondria and so, studies concentrated on the mitochondrial ACO. The <scene name='Aconitase/7acn-sf4-3cys/1'>(4Fe-4S) cofactor is held in place</scene> by three sulfur atoms belonging to the cysteins-385, -448, and -451.
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<!--It is clear that, in order to synthesize L-isocitrate, stereoselective catalysis must occur.-->
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== Cytosolic aconitase and its other function ==
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<applet load='Morph_2ipy-2b3x.pdb.gz' scene='Aconitase/2ipy-total/2' size='400' frame='true' align='right' caption="Cytosolic aconitase from rabbit (bound to RNA) and human (with Fe4S4 cluster), from PDB [[2ipy]] and [[2b3x]]." />A specialty of cAc is that in mammals it has developed a <scene name='Aconitase/2ipy-total/2'>second function</scene> as inhibitor of <scene name='Aconitase/2ipy-rna/1'>those mRNA</scene> that carry an <scene name='Aconitase/2ipy-rna-ire/1'>iron-responsive element (IRE)</scene>. Therefore, the cytosolic cAc is named IREBP for IRE-binding protein when this function is talked about. Only one of the two functions is active, depending on whether <scene name='Aconitase/2b3x-cluster/1'>the (4Fe-4S) cofactor</scene> is present in the molecule: it's essential for <scene name='Aconitase/2b3x-total/1'>the ACO function</scene>. You can see, by <scene name='Aconitase/Morph/2'>looking at the morph</scene>, how much the enzyme structure differs between those two functions.
<!--== Available structures ==
<!--== Available structures ==
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*[[2ipy]] - cAc (''Oryctolagus cuniculus'') as IRP1 with ferritin RNA
*[[2ipy]] - cAc (''Oryctolagus cuniculus'') as IRP1 with ferritin RNA
*[[5acn]] - mAc (''Sus scrofa'') with Fe3S4 (missing a Fe)
*[[5acn]] - mAc (''Sus scrofa'') with Fe3S4 (missing a Fe)
-
*[[6acn]] - mAc (''Sus scrofa'') with Fe4S4
+
*[[6acn]] - mAc (''Sus scrofa'') with tricarballylic acid
*[[7acn]] - mAc (''Sus scrofa'') with isocitrate
*[[7acn]] - mAc (''Sus scrofa'') with isocitrate
*[[8acn]] - mAc (''Sus scrofa'') with nitroisocitrate
*[[8acn]] - mAc (''Sus scrofa'') with nitroisocitrate

Revision as of 16:34, 18 February 2009

Aconitase (ACO) is an enzymatic domain that confers the ability to catalyse the equilibrium

citrate = aconitate + H2O = L-isocitrate

This reaction is part of the citrate (TCA-, Krebs-)cycle.

In most organims, there is a cytosolic enzyme with an ACO domain (cAc), and in eukaryotes, a second copy of it was introduced with mitochondria (mAc). Plants developed even more copies in mitochondria.

Catalytic mechanism of mitochondrial ACO

Mitochondrial aconitase from pig, PDB 7acn.

Drag the structure with the mouse to rotate
The bulk of citrate cycle processing happens in mitochondria and so, studies concentrated on the mitochondrial ACO. The by three sulfur atoms belonging to the cysteins-385, -448, and -451.


Cytosolic aconitase and its other function

Cytosolic aconitase from rabbit (bound to RNA) and human (with Fe4S4 cluster), from PDB 2ipy and 2b3x.

Drag the structure with the mouse to rotate
A specialty of cAc is that in mammals it has developed a as inhibitor of that carry an . Therefore, the cytosolic cAc is named IREBP for IRE-binding protein when this function is talked about. Only one of the two functions is active, depending on whether is present in the molecule: it's essential for . You can see, by , how much the enzyme structure differs between those two functions.

Weblinks

Retrieved from "http://52.214.119.220/wiki/index.php/Aconitase"
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