HW Lecture #21: Control of Glycolysis and the Pentose Phosphate Pathway

HW: pg. 424 (study exercises 3,4); (Problems 7, 8, 10, 11) AND one suggested question with answer for quiz #2. Optional HW: pg. 424, problem 9

Pg. 424

  1. Primary mechanisms that regulate phosphofructokinase are allosteric effects and substrate cycling. ATP binds to a substrate site and an allosteric site. Binding of ATP to the allosteric site stabilizes the T (inactive) conformation and prevents F6P from binding. In otherwords, ATP shifts the PFK activity curve to the RIGHT in a cooperative manner. In the presence of ATP, PFK has a lower affinity for its substrate than in the absence of ATP. Affinity of PFK for its substrate (F6P) is increased in the presence of AMP (curve shifts to the left) because AMP causes the enzyme to switch to its R (active) conformation which has a higher affinity for PFK.
  2. The metabolic advantage of a substrate cycle is immediate ability to increase or decrease flux in two opposing pathways; i.e., control!