lecture_22legge

lecture_22legge - 11/13/2009 Glycolysis II 11/05/09 Front...

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11/13/2009 1 Glycolysis II 11/05/09 Front half of glycolysis Aldolase with a Tyr residue acting as a proton donor / acceptor Aldolase with an Asp residue acting as a proton donor / acceptor (current text book) Triosephosphate isomerase DHAP GAP [ ] 96 1 10 x 7 . 4 DHAP GAP K 2 eq = = = [ ] TIM is a perfect enzyme which its rate is diffusion controlled. A rapid equilibrium allows GAP to be used and DHAP to replace the used GAP .
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11/13/2009 2 TIM has an enediol intermediate H C O CH 2 OPO 3 2- O H H C CH 2 OPO 3 2- O H C C CH 2 OPO 3 2- O O H H H H O H Transition state analogues Phosphoglycohydroxamate (A) and 2-phosphoglycolate (B) bind to TIM 155 and 100 times stronger than GAP of DHAP GAP enediol DHAP CH 2 OPO 3 2- O - N OH C O 3 2- POH 2 C O - H H O O 3 2- POH 2 C O - O A. B. TIM has an extended “low barrier” hydrogen bond transition state Hydrogen bonds have unusually strong interactions and have lead to pK of Glu 165 to shift from 4.1 to 6.5 and the pK of Geometry of the enediol intermediate prevents formation of methyl glyoxal
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lecture_22legge - 11/13/2009 Glycolysis II 11/05/09 Front...

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