glycolysis ii 11 05 09 n.
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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 .

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slide4

Aldolase

with a Tyr

residue acting as a proton donor / acceptor

slide5

Aldolase

with an Asp

residue acting as a proton donor / acceptor

(current text book)

triosephosphate isomerase
Triosephosphate isomerase

DHAP GAP

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.

tim has an enediol intermediate
TIM has an enediol intermediate

GAP

enediol

DHAP

Transition state analogues Phosphoglycohydroxamate (A) and 2-phosphoglycolate (B) bind to TIM 155 and 100 times stronger than GAP of DHAP

B.

A.

tim has an extended low barrier hydrogen bond transition state
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
Geometry of the enediol intermediate prevents formation of methyl glyoxal

Orbital symmetry prevents double bond formation needed for methyl glyoxal

glyceraldehyde 3 phosphate dehydrogenase
Glyceraldehyde-3-phosphate dehydrogenase

The first high-energy intermediate

+NAD+ + Pi

+ NADH

Uses inorganic phosphate to create 1,3 bisphosphoglycerate

mechanistic steps for gapdh
Mechanistic steps for GAPDH

1. GAP binds to enzyme.

2. The nucleophile SH attacks aldehyde to make a thiohemiacetal.

3. Thiohemiacetal undergoes oxidation to an acyl thioester by a direct transfer of electrons to NAD+ to form NADH.

4. NADH comes off and NAD+ comes on.

5. Thioester undergoes nucleophilic attack by Pi to form 1,3 BPG.

The acid anhydride of phosphate in a high energy phosphate intermediate

slide18

GAP + Pi + NAD+ 1,3 -BPG + NADH + 6.7 kJ• mol-1

1,3 BPG + ADP 3PG + ATP -18.8 kJ• mol-1

GAP+Pi+NAD+ +ADP 3PG+NADH+ATP -12.1 kJ•mol-1

slide20

Phosphoglycerate mutase requires a phosphorylated form of the enzyme to be active. Only 2,3 BPG can phosphorylate the unphosphorylated enzyme.

Phospho Histidine residue

glycolysis influences oxygen transport
Glycolysis influences oxygen transport

Oxygen saturation curves in erythrocytes

enolase generation of a second high energy intermediate
Enolase generation of a second “high energy” intermediate

+ H2O

2 PhosphoglyceratePhosphoenol pyruvate