The shape of the enzyme determines which reaction it can catalyze.
Explanation:
The enzymes are highly specific in nature. They catalyze the biological reactions by lowering their activation energy and thus accelerating the chemical reaction taking place.
The shape of enzymes plays a key role in its function as it has specific substrate binding sites, with which it would form an enzyme-substrate complex. Change in the shape will also alter the active sites and consequently, enzyme is dysfunctional.