Answer the following question given this paragraph: 

In eukaryotic cells, most of the intracellular proteins that are activated by a ligand binding to a receptor protein are enzymes. Receptor proteins are named after the type of enzyme that they interact with inside the cell. These enzymes include G proteins and protein kinases, likewise there are G-protein-linked receptors and tyrosine kinase receptors. A kinase is a protein involved in phosphorylation. Tyrosine kinase receptors bind many polypeptide growth factors, cytokines, and hormones. Once the ligand is bound, these receptors specifically phosphorylate tyrosine amino acids, activating the signal transduction process inside the cell.


Q: What is named after the type of enzyme they interact with in the cell?


A:
receptor proteins