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Triose Phosphate Isomerase (TIM) uses acid/base catalysis to move the carbonyl from C2 to C1

Triose Phosphate Isomerase (TIM) uses acid/base catalysis to move the carbonyl from C2 to C1. GAP dehydrogenase oxidizes an aldehyde to thioester and then displaces with phosphate to make a high energy phosphoanhydride.

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Triose Phosphate Isomerase (TIM) uses acid/base catalysis to move the carbonyl from C2 to C1

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  1. Triose Phosphate Isomerase (TIM) uses acid/base catalysis to move the carbonyl from C2 to C1

  2. GAP dehydrogenase oxidizes an aldehyde to thioester and then displaces with phosphate to make a high energy phosphoanhydride An aldehyde cannot be oxidized by hydride transfer, but a thiohemiacetal can. The product thioester captures some of the energy of oxidation in the high energy C-S bond.

  3. GAP dehydrogenase oxidizes an aldehyde to thioester and then displaces with phosphate to make a high energy phosphoanhydride The thioester is sufficiently reactive that even a poor nucleophile such as a phosphate ion can react and displace the catalytic cysteine residue.

  4. Phosphoglycerate kinase is a reversible phosphoryl transfer to ADP The energy of the phosphoanhydride bond can be captured by transferring the phosphate to ADP, generating an equally high energy phosphodiester bond

  5. 3-Phosphoglycerate mutase moves a phosphate through “sleight of hand” How does the first phosphate get on the enzyme? How stable do you think a phosphohistidine bond is?

  6. Enolase generates the high energy phosporylated enolate phosphoenolpyruvate Two Mg2+ ions help to stabilize negative charge through electrostatic attractions Deprotonation of the C position leads to an elimination of water by a E1cB mechanism PEP is a very high energy phosphate ester because the enolate leaving group can immediately isomerize to a ketone

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