MCAT® ExamBiological and Biochemical Foundations of Living SystemsEasy
A researcher is studying a novel protein that exhibits increased activity when phosphorylated by a specific kinase. This phosphorylation event primarily leads to a conformational change in the protein, exposing its active site. What type of enzyme regulation is best exemplified by this scenario?
- ACompetitive inhibition
- BCovalent modification
- CAllosteric regulation
- DFeedback inhibition
Show answer & explanationAnswer & explanation
Correct answer: B. Covalent modification
The scenario describes phosphorylation, which is a common type of covalent modification that alters protein activity. This modification leads to a conformational change, directly affecting the enzyme's function.
Why the other options are wrong
- A. Competitive inhibition involves an inhibitor binding to the active site, competing with the substrate.
- C. Allosteric regulation involves non-covalent binding of a molecule to a site other than the active site, inducing a conformational change.
- D. Feedback inhibition is a type of allosteric regulation where the end product of a metabolic pathway inhibits an enzyme early in the pathway.
Covalent Modification
Covalent modification is a type of enzyme regulation where a chemical group is added to or removed from an enzyme via a covalent bond, leading to a change in its activity.
- Common examples include phosphorylation/dephosphorylation.
- Often involves kinases (adding phosphate) and phosphatases (removing phosphate).
- Can activate or inactivate an enzyme.
Memory trick: Enzymes can be regulated by many 'MODS' to their activity.