Biochemistry 4th Edition by Christopher Mathews,Kensal van Holde, Dean Appling, Spencer Anthony Cahill

Exercise 6

Consider the following hypothetical metabolic pathway:
(a) Under intracellular conditions, the activity of enzyme X is 100 pmol/l0 6 cells/sec. Calculate the effect on metabolic flux rate (pmol/10 6 cells/sec) of B C of the following treatments. Calculate as % change (increase or decrease).
Treatment % Change in flux
Inhibitor that reduces activity of X by 10% Activator that increases activity of X by 10%
(b) Now consider a substrate cycle operating with enzymes X and Y in the same hypothetical metabolic pathway:
Under intracellular conditions, the activity of enzyme X is 100 pmol/10 6 cells/sec, and that of enzyme Y is 80 pmol/10 6 cells/ sec. What are the direction and rate (pmol/10 6 cells/sec) of metabolic flux between B and C
(c) Calculate the effect on direction and metabolic flux rate of the following treatments. Calculate as % change (increase or decrease). (d) Briefly summarize the regulatory advantage(s) of a substrate cycle in a pathway.