Triose Phosphate Isomerase: Difference between revisions

Proteopedia Page Contributors and Editors (what is this?)Proteopedia Page Contributors and Editors (what is this?)

Gregg Snider, Stephen Everse, Eran Hodis, David Canner, Eric Martz, Michal Harel, Alexander Berchansky, Jane S. Richardson, Angel Herraez

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 [[Image:classical2.png|left|thumb|500px| '''Classic Mechanism proposed by Knowles and co-workers''']]
-TPI carries out the isomerization reaction through an acid-base-mediated mechanism involving '''three catalytic residues''' (<scene name='Triose_Phosphate_Isomerase/Three_catalytic_residues1/2'>restore initial scene</scene>), each of which <scene name='Triose_Phosphate_Isomerase/Three_catalytic_residues2/1'>contacts the substrate</scene>.  First, the DHAP or GAP substrate is initially attracted to the enzyme active site through '''electrostatic interactions''' between the negatively charged phosphate group of the substrate and the positively charged '''Lys12''', with the resulting interaction stabilizing the substrate.
+TPI carries out the isomerization reaction through an acid-base-mediated mechanism involving (<scene name='Triose_Phosphate_Isomerase/Three_catalytic_residues1/2'>three catalytic residues</scene>), each of which <scene name='Triose_Phosphate_Isomerase/Three_catalytic_residues2/1'>contacts the substrate</scene>.  First, the DHAP or GAP substrate is initially attracted to the enzyme active site through '''electrostatic interactions''' between the negatively charged phosphate group of the substrate and the positively charged '''Lys12''', with the resulting interaction stabilizing the substrate.
 According to the "classic" mechanism, '''Glu165''' plays the role of the '''general base''' catalyst by abstracting a proton from the pro(''R'') position of carbon 1 of DHAP or the C-2 proton of GAP. However, the carboxylate group of Glutamate 165 alone does not possess the basicity to abstract a proton and requires
 '''His95''', the '''general acid''', to donate a proton to stabilize the negative charge building up on C-2 carbonyl oxygen, effectively stabilizing the planar endediol(ate) intermediate.  Lys12 and Asn11 also function to stabilize the negative charge which builds up on this intermediate.