MCAT Content / Biosignalling / Receptor Enzymes

Receptor enzymes

Topic: Biosignalling

Receptor enzymes are cell-surface receptors where the binding of an extracellular ligand result in an enzymatic reaction inside the cell.

Receptors enzymes or enzyme-linked receptors are cell-surface receptors with intracellular domains that are associated with an enzyme. In some cases, the intracellular domain of the receptor itself is an enzyme, or the enzyme-linked receptor has an intracellular domain that interacts directly with an enzyme. The enzyme-linked receptors usually have large extracellular and intracellular domains, but the membrane-spanning region consists of a single alpha-helical region of the peptide strand. When a ligand binds to the extracellular domain, a signal is transferred through the membrane and activates the enzyme. This ligand binding sets off a chain of events within the cell that eventually leads to a response.

An example of this type of enzyme-linked receptor is the tyrosine kinase receptor. The tyrosine kinase receptor transfers phosphate groups from ATP to tyrosine molecules. Signaling molecules bind to the extracellular domain of two nearby tyrosine kinase receptors, which then dimerize. Phosphates are then added to tyrosine residues on the intracellular domain of the receptors and can then transmit the signal to the next messenger within the cytoplasm. The misregulation of tyrosine kinase receptor signaling is linked to many types of cancer and is a common drug target.

Practice Questions

Khan Academy

Biochemistry of a newly discovered (pretend) neurotransmitter 

Reducing pain with morphine

The role of tyrosine-kinase inhibitors in preventing cancer

Chronic myelogenous leukemia and the Philadelphia chromosome

MCAT Official Prep (AAMC)

Section Bank B/B Section Passage 4 Question 27

Key Points

• Enzyme-linked receptors (AKA receptor enzymes) are cell-surface receptors with intracellular domains that are associated with an enzyme.

Key Terms

enzyme: A protein that acts as a catalyst, increasing the rate of a chemical reaction

cell surface receptors: receptors that are embedded in the plasma membrane of cells

intracellular: located within the cell

extracellular: located outside the cell

tyrosine kinase: an enzyme that can transfer a phosphate group from ATP to a protein in a cell

dimerize: coming together of two monomers joined by bonds

tyrosine: a common amino acid

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