Triose Phosphate Isomerase: Difference between revisions
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The formation and stabilization of the enediol(ate) intermediate has been a source of great discussion amongst scientists in the field. This is due to the fact that the formation of the enediol(ate) intermediate presents a large thermodynamic barrier involving the abstraction of the α-proton from the carbon acid substrate, an unfavorable process due to the lack of acidity and high p''K''a of the C1 proton of the substrate. The "classic" mechanism (shown above) put forth by Knowles and co-workers stated that the kinetic barrier is overcome by the concerted deprotonation of the C1 and the protonation of the C2 carbonyl oxygen which would effectively allow for equivalent free energies for each species shown shown, thus promoting an equilibrium constant near unity.<ref>PMID:9398185</ref> This concept of preferential binding arising from matching of the reaction energy barriers is a common theme of enzyme catalysis <ref>PMID:17287353</ref>. | The formation and stabilization of the enediol(ate) intermediate has been a source of great discussion amongst scientists in the field. This is due to the fact that the formation of the enediol(ate) intermediate presents a large thermodynamic barrier involving the abstraction of the α-proton from the carbon acid substrate, an unfavorable process due to the lack of acidity and high p''K''a of the C1 proton of the substrate. The "classic" mechanism (shown above) put forth by Knowles and co-workers stated that the kinetic barrier is overcome by the concerted deprotonation of the C1 and the protonation of the C2 carbonyl oxygen which would effectively allow for equivalent free energies for each species shown shown, thus promoting an equilibrium constant near unity.<ref>PMID:9398185</ref> This concept of preferential binding arising from matching of the reaction energy barriers is a common theme of enzyme catalysis <ref>PMID:17287353</ref>. | ||
[[Image:TPIfreeenergy2png.png|left|thumb|300px| '''Free-Energy Profile for the Reaction Catalyzed by Triosephosphate Isomerase''']] | [[Image:TPIfreeenergy2png.png|left|thumb|300px| '''Free-Energy Profile for the Reaction Catalyzed by Triosephosphate Isomerase''']] | ||
=== Low-Barrier Hydrogen Bond in the TPI Mechanism=== | === Low-Barrier Hydrogen Bond in the TPI Mechanism=== | ||
[[Image:LBHB1_2.png|thumb|right|400px| '''Proposed LBHB between Histidine and Enediol Intermediate'''.]] | [[Image:LBHB1_2.png|thumb|right|400px| '''Proposed LBHB between Histidine and Enediol Intermediate'''.]] | ||