Allen sandbox 1: Difference between revisions

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[[Image:mechanism.png|left|400px|The mechanism of 2PG to PEP using enolase.]]<ref>{{website2}}</ref>
[[Image:mechanism.png|left|400px|The mechanism of 2PG to PEP using enolase.]]<ref>{{website2}}</ref>
The   
The   
<scene name='Cory_Tiedeman_Sandbox_1/Active_site/1'>active site</scene> of enolase as shown, involves Lys 345, Lys 396, Glu 168, Glu 211, and His 159.  Enolase forms a complex with two   
<scene name='Cory_Tiedeman_Sandbox_1/Active_site/1'>active site</scene> of enolase includes the residues Lys 345, Lys 396, Glu 168, Glu 211, and His 159.  Enolase forms a complex with two   
<scene name='Cory_Tiedeman_Sandbox_1/Mg/3'>Mg 2+'s</scene> at its active site.   
<scene name='Cory_Tiedeman_Sandbox_1/Mg/3'>Mg 2+'s</scene> at its active site.
The substrate, 2PG, binds to the two <scene name='Cory_Tiedeman_Sandbox_1/Mechanism/4'>Mg2+'s, Glu 211, and Lys 345</scene>. The Mg 2+ then forms a bond at the deprotonated carboxylic acid on the 1'C to connect it with enolase.  It also is connected to Glu 211 and Lys 345.  Glu 211 makes a hydrogen bond with the alcohol group on the 3'C. Lys 345 deprotonates the 2'C and then the 2'C forms an alkene with the 1'C which then moves the electrons forming the ketone onto the oxygen, giving it a negative charge. The other oxygen, which already has a negative charge, then moves its electron to form a ketone with the 1'C. The electrons that made up the alkene between the 1'C adn 2'C then moves to form an alkene between the 2'C and 3'C. This breaks the bond with the alcohol on the 3'C which deprotonates Glu 211 on enolase to form a water molecule.  Then the new molecule is released from enolase as PEP. PEP then goes on through another step in glycolysis to create pyruvate.   
The mechanism of enolase follows 3 steps:  
Step 1: The substrate, 2PG, binds to the two <scene name='Cory_Tiedeman_Sandbox_1/Mechanism/4'>Mg2+'s</scene>. The carboxyl group coordinates with the two magnesium ions, which stabilizes the negative charge on the oxygen atom and removes charge from the alpha hydrogen, making it a better leaving group.
Step 2: Lys 345 then deprotonates the alpha hydrogen, a reaction which is stabilized by resonance between the carboxyl oxygens and the two Mg ions, in addition to the stabilizing effect of Glu 211 bonded to the hydroxyl group. This creates a carbanion intermediate.  
Step 3: An electron transfer reaction then occurs from the C'1 carboxyl oxygen to form a ketone. This removes electrons from the alkene bond between C'1 and C'2 to create an alkene between C'2 and C'3 instead. This allows the C'3 hydroxyl group to deprotonate Glu 211, resulting in the ejection of a water molecule and the product PEP. PEP then continues in glycolysis to create pyruvate.   


Fluoride ions inhibits glycolysis by forming a bond with Mg 2+, thus blocking the substrate (2PG) from binding to the active site of enolase.<ref>{{textbook |author=Voet, Donald; Voet, Judith C.; Pratt, Charlotte W.|title=Fundamentals of Biochemistry: Life at the Molecular Level|edition= 3|pages=500|}}</ref>
Fluoride ions inhibits glycolysis by forming a bond with Mg 2+, thus blocking the substrate (2PG) from binding to the active site of enolase.<ref>{{textbook |author=Voet, Donald; Voet, Judith C.; Pratt, Charlotte W.|title=Fundamentals of Biochemistry: Life at the Molecular Level|edition= 3|pages=500|}}</ref>
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