Question

The joint pain and swelling associated with Gout is caused by hyperuricemia, the accumulation of uric acid in the joints. The final step in the synthesis of uric acid is catalyzed by the enzyme xanthine oxidase.Gout can be treated by administering ALLOPURINOL, and inhibitor of xanthine oxidase.draw a line on the Lineweaver-Burke plot provided indicating how you predict that the presence of allopurinol would influence the kinetic behavior of this enzyme. (Please explain how you got the graph)

Answer 1

Allopurinol shows competative inhibition at low concentration and shows  non-competitive inhibition of xanthine oxidase at high concentration. Thats why we will analyse both graphs ----

At low Conc. Allopurinol inhibits Xanthine oxidase as a competatve inhibitor so Vmax(reaction velocity = 1/Vmax) will be same and Km increases and overall turnover of the reaction will be unchanged. On increaing Allopurinal conc. Km futher increases.

whereas at high Conc. Allopurinol inhibits Xanthine oxidase as a non-competatve inhibitor so Vmax(reaction velocity = 1/Vmax) decreases and Km remains same. On increaing Allopurinal conc. Vmax futher decreases.