6_glycolysis_pt1

Phsophofructokinase 1 pfk 1 g 142

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Unformatted text preview: dolase •  Chemical logic: reverse aldol condensaZon; two mechanisms (class I & class II) for stabilizing the enolate intermediate (Schiff base and Zn2+) •  Pathway logic: ring spligng; takes advantage of C2 carbonyl (PGI product, step II) •  Driving force: product removal overcomes unfavorable ΔG´° •  Noteworthy Addi8ons: TIM barrel fold used in apparent convergent evoluZon of class I and class II enzymes V. Triose Phosphate Isomerase (TIM) ΔG´° = 7.5 kJ/mol •  ReacZon proceeds through an enediol intermediate •  Rate is diffusion ­limited (means what?) •  For which the TIM ­barrel fold was named Write a plausible reac1on mechanism V. Triose Phosphate Isomerase (TIM) PDB 2VXN TIM Barrel: 8 ­stranded parallel beta sheet connected by 8 helices Summary TIM •  Chemical logic: stabilizes enediol intermediate •  Pathway logic: coverts 3 ­carbon compounds to the common form used in the next step •  Driving force: highly reversible •  Noteworthy Addi8ons: The original TIM barrel; extremely efficient enzyme Summary: Preparatory Phase (–2 ATP) ΔG´° (kJ/mol)  ­16.7 1.7  ­14.2 23.8 7.5 Why is the overall direction forward?...
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