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Reaction six substrate and products
- (Glyceraldehyde-3-phosphate)x2(1,3-Bisphosphoglycerate)x2
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ΔG'° of reaction six
6.3 KJ mol-1
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Why is glyceraldehyde-3-phosphate important?
It is the first high energy intermediate
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Key residues of glyceraldehyde-3-phosphate deyhydrogenase
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Reaction six mechanism
- 1. Cysteine's -S-H donates electrons to C3 resulting in tautomerization of C3=O to C3-O:-2. C3 donates it's proton to NAD+ reforming the C3=O bond
- 3. NADH is exchanged for NAD+
- 4. Pi-O:- attacks S-C3=O, histidine donates it's proton to cysteine's -S:-5. 1,3-Bisphosphoglycerate is eliminated
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How are phosphoglycerate kinase and hexokinase similar?
- Both kinases
- Both swing shut upon allosteric binding
- - Exclude water
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What does phosphoglycerate kinase do?
- Removes Pi from 1,3-bisphosphate carbon 1, and phosphorylates ADP
- Produces 3-phosphoglycerate as a biproduct
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ΔG'° of reaction seven
-18.5 KJ mol-1
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Mechanism of reaction seven
- a. Mg2+ coordinates ADP's α and β phoshates
- b. β-phosphate attacks phosphate on 1,3-BPG's C1, causing the O-P oxygen to draw electrons from the bond
- c. ATP is formed
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Substrate and products of reaction eight
- 3-phosphoglycerate
- 2-Phosphoglycerate
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Thing to know about reaction eight
- Reversible
- Mg2+ required
- Specific amounts of 2,3-BPG are required for enzyme function
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ΔG'° of reaction eight
4.4 KJ mol-1
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Key residue for phosphoglycerate mutase
Histidine
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Mechanism of reaction eight
- 1. Phosphorylated histidine phosphorylates C2-OH
- 2. C3-P rephosphorylates His
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Reaction eight's tangential reaction (include enzyme and product)
- 1,3-BPG -> 2,3-Bisphosphoglycerate
- Via bisphosphoglycerate mutase
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Enzyme converting 2,3-Bisphosphoglycerate to 3-phosphoglycerate
2,3-Bisphosphoglycerate phosphatase
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Why is 2,3-Bisphosphoglycerate important?
Binds to deoxyhemoglobin and influences O2 affinity
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Where does synthesis and degradation of 2,3-Bisphosphoglycerate occur
Erythrocytes
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Reaction nine substrate and products
- 2-phosphoglycerate
- Phosphoenolpyruvate
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ΔG'° of reaction nine
7.5 KJ mol-1
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Mechanism of reaction nine
- i. Two Mg2+ ions coordinate the C1 carboxyl group
- 1. Lysine abstracts proton C2-H, forming a terminal enol intermediate R-C2=COO2-(Mg2+)x2
- 2. Glutamate deprotonates causing water to leave from the C3, allowing formation of phosphoenolpyruvate
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Why is fluorine an inhibitor of enolase?
It can bind to the Mg2+ ions
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Products and substrates of reaction ten
- Phosphoenol pyruvate, ADP
- Pyruvate, ATP
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ΔG'° of reaction ten
-31.4 KJ mol-1
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Key requirements for reaction ten
Two Mg2+ ions (one for ADP, one for PEP)
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Basic steps of reaction ten
- 1. Depshophorylation of PEP (ADP->ATP)
- 2. Tautomerization of Enolpyruvate
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