Biochemistry 4th Edition by Reginald Garrett, Charles Grisham

Exercise 6

Predict the effect of caffeine consumption on glycogen phosphorylase activity
The cAMP formed by adenylyl cyclase (Figure 15.19) does not persist because 5'-phosphodiesterase activity prevalent in cells hydrolyzes cAMP to give 5'AMP. Caffeine inhibits 5'-phosphodiesterase activity. Describe the effects on glycogen phosphorylase activity that arise as a consequence of drinking lots of caffeinated coffee.