Explain the difference between Fischer's lock-and-key theory and Koshland's induced fit hypothesis of enzyme-substrate interaction.

The lock-and-key theory suggests that enzymes are flexible and change their shape to accommodate substrates, while the induced fit hypothesis proposes that enzymes have rigid active sites perfectly shaped for specific substrates.

In the lock-and-key theory, substrate binding alters the enzyme's shape to create a better fit, whereas in the induced fit hypothesis, substrates fit into enzymes without changing their shape.

The lock-and-key theory posits that an enzyme's active site is specifically shaped to perfectly accommodate a particular substrate without any alteration in its structure, while according to the induced-fit hypothesis, an enzyme changes its conformation upon substrate binding for a snugger interaction.

Both theories propose that enzymes change their shapes upon substrate binding.