Enzyme Inhibition — Overview & Types

Enzyme X normally has a reaction rate of 500 units per minute. Molecule B is added to the cell culture. After a few minutes, the cell culture is observed and the reaction rate has now increased to 653 units per minute.

But after a while longer, you notice that the reaction rate has gone down to zero units per minute. You run some tests and find that molecule B is completely gone from the reaction mixture! What type of molecule is molecule B?