An enzyme-linked receptor, also known as a catalytic receptor, is a transmembrane receptor, where the binding of an extracellular ligand causes enzymatic activity on the intracellular side.[1] Hence a catalytic receptor is an integral membrane protein possessing both catalytic, and receptor functions.[2]
They have two important domains, an extra-cellular ligand binding domain and an intracellular domain, which has a catalytic function; and a single transmembrane helix. The signaling molecule binds to the receptor on the outside of the cell and causes a conformational change on the catalytic function located on the receptor inside the cell.
Examples of the enzymatic activity include:
The following is a list of the five major families of catalytic receptors:
| Family | Member | Gene | Catalytic activity | Endogenous ligands | Synthetic ligands |
|---|---|---|---|---|---|
| Erb[4] | ErbB1 (epidermal growth factor receptor) | EGFR | tyrosine kinase EC 2.7.10.1 | Epidermal growth factor, amphiregulin, betacellulin, epigen, epiregulin, HB-EGF, TGFa | GW583340, gefitinib, erlotinib, tyrphostins AG879 and AG1478 |
| ErbB2 | ERBB2 | " | |||
| ErbB3 | ERBB3 | " | NRG-1, NRG-2 | GW583340, gefitinib, erlotinib, tyrphostins AG879 and AG1478 | |
| ErbB4 | ERBB4 | " | Betacellulin, epiregulin, HB-EGF, NRG-1, NRG-2, NRG-3, NRG-4 | GW583340, gefitinib, erlotinib, tyrphostins AG879 and AG1478 | |
| GDNF (glial cell-derived neurotrophic factor)[5] | GFRa1 | GFRa1 | " | GDNF > neurturin > artemin | |
| GFRa2 | GFRa2 | " | Neurturin > GDNF | ||
| GFRa3 | GFRa3 | " | Artemin | ||
| GFRa4 | GFRa4 | " | Persephin | ||
| NPR (natriuretic peptide receptor)[6] | NPR1 | NPR1 | guanylyl cyclase EC 4.6.1.2 | Atrial natriuretic peptide | |
| NPR2 | NPR2 | " | C-type natriuretic peptide | ||
| NPR3 | NPR3 | " | Atrial natriuretic peptide | ||
| NPR4 | NPR4 | " | Uroguanylin | ||
| trk neurotrophin receptor[7] | TrkA | NTRK1 | tyrosine kinase EC 2.7.10.1 | Nerve growth factor > NT-3 | GW441756, tyrphostin AG879 |
| TrkB | NTRK2 | " | Brain-derived neurotrophic factor, NT-4/NT-5 > NT-3 | ||
| TrkC | NTRK3 | " | NT-3 | ||
| p75 | NGFR | " | NGF, BDNF, NT3, NT4/5 | ||
| Toll-like[8] | TLR1 | TLR1 | " | ||
| TLR2 | TLR2 | " | Peptidoglycan | ||
| TLR3 | TLR3 | " | polyIC, polyinosine-polycytosine | ||
| TLR4 | TLR4 | " | LPS, lipopolysaccharide derived from Gram-negative bacteria | ||
| TLR5 | TLR5 | " | Flagellin | ||
| TLR6 | TLR6 | " | |||
| TLR7 | TLR7 | " | resiquimod, imiquimod | ||
| TLR8 | TLR8 | " | |||
| TLR9 | TLR9 | " | CpG, DNA enriched in cytosine:guanosine pairs | ||
| TLR10 | TLR10 | " |