The Biochemistry of Movement > 9.7.4. Proteins are used as both structural molecules and enzymes to catalyse metabolic reactions > Why an Enzyme’s Binding Site is Substrate Specific >
Using a named example of an enzyme, explain why the enzyme’s binding site is substrate specific
- Initially, scientists looked at enzymes and substrates with a “lock and key” type of vision. This stated that the enzyme and substrate fit together perfectly like puzzle pieces.
- Today, the “induced fit” model is more widely accepted and researched. This model states that when the substrate and enzyme come together, there is a slight shift in the enzyme’s structure and it contorts the substrate slightly into a transition straight, which increases the rate of reaction.
- Lactose is a relatively large disaccharide. Due to its size, it must be broken down into smaller components before it can be properly digested. The small intestine produces the lactase enzyme. Upon attachment to lactose, the enzyme hydrolyses it into glucose and galactose. There are no other substrates that will bind to lactase, and no other enzymes that will break down lactose. This is why those who are lactose intolerant are unable to digest milk.