Final answer:
Enzyme activity can decrease over time even at high substrate concentrations due to non-competitive inhibition, where the inhibitor changes the enzyme's conformation, affecting its functionality regardless of substrate concentration.
Step-by-step explanation:
The type of inhibition that explains why enzyme activity will decrease over time even at very high substrate concentrations is non-competitive inhibition. Non-competitive inhibitors can bind to either the free enzyme or the enzyme-substrate complex because their binding site is distinct from the active site. Binding of non-competitive inhibitors alters the conformation of the enzyme and changes the configuration of the active site. Consequently, either the enzyme-substrate complex does not form at its normal rate, or, once formed, it does not yield products at the normal rate. This form of inhibition cannot be overcome by increasing substrate concentration, as the inhibitor is not in direct competition with the substrate for the active site.