Tyrosine Kinase Pathway Practice Test

Receptor tyrosine kinases (RTKs) transduce extracellular signals into intracellular signaling cascades. This is possible because RTKs have an extracellular ligand binding domain to sense ligands outside of the cell, a transmembrane domain that spans the cell membrane, and an intracellular domain that activates pathways within the cell.

Which of the following best describesthe mechanism by which the cytosolic domains of RTKs activate downstream signaling cascades?

Protein-tyrosine kinase activation can result in the activation of two classical second messengers, inositol triphosphate (IP3) and diacylglycerol (DAG). These molecules are produced as a result of a hydrolysis reaction that is stimulated by protein-tyrosine kinase activation.

What is the enzyme that catalyzes this hydrolysis reaction, and what molecule is cleaved into IP3 and DAG?