Enzyme-linked receptor
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. Hence a catalytic receptor is an integral membrane protein possessing both enzymatic catalytic and receptor functions.
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:
- Receptor tyrosine kinase, as in fibroblast growth factor receptor. Most enzyme-linked receptors are of this type.
- Serine/threonine-specific protein kinase, as in bone morphogenetic protein
- Guanylate cyclase, as in atrial natriuretic factor receptor
Types
| Family | Member | Gene | Catalytic activity | Endogenous ligands | Synthetic ligands |
| Erb | ErbB1 | tyrosine kinase | Epidermal growth factor, amphiregulin, betacellulin, epigen, epiregulin, HB-EGF, TGFa | GW583340, gefitinib, erlotinib, tyrphostins AG879 and AG1478 | |
| Erb | ErbB2 | " | |||
| Erb | ErbB3 | " | NRG-1, NRG-2 | GW583340, gefitinib, erlotinib, tyrphostins AG879 and AG1478 | |
| Erb | ErbB4 | " | Betacellulin, epiregulin, HB-EGF, NRG-1, NRG-2, NRG-3, NRG-4 | GW583340, gefitinib, erlotinib, tyrphostins AG879 and AG1478 | |
| GDNF | GFRa1 | " | GDNF > neurturin > artemin | ||
| GDNF | GFRa2 | " | Neurturin > GDNF | ||
| GDNF | GFRa3 | " | Artemin | ||
| GDNF | GFRa4 | " | Persephin | ||
| NPR | NPR1 | guanylyl cyclase | Atrial natriuretic peptide | ||
| NPR | NPR2 | " | C-type natriuretic peptide | ||
| NPR | NPR3 | " | Atrial natriuretic peptide | ||
| NPR | NPR4 | " | Uroguanylin | ||
| trk neurotrophin receptor | TrkA | tyrosine kinase | Nerve growth factor > NT-3 | GW441756, tyrphostin AG879 | |
| trk neurotrophin receptor | TrkB | " | Brain-derived neurotrophic factor, NT-4/NT-5 > NT-3 | ||
| trk neurotrophin receptor | TrkC | " | NT-3 | ||
| trk neurotrophin receptor | p75 | " | NGF, BDNF, NT3, NT4/5 | ||
| Toll-like | TLR1 | " | |||
| Toll-like | TLR2 | " | Peptidoglycan | ||
| Toll-like | TLR3 | " | polyIC, polyinosine-polycytosine | ||
| Toll-like | TLR4 | " | LPS, lipopolysaccharide derived from Gram-negative bacteria | ||
| Toll-like | TLR5 | " | Flagellin | ||
| Toll-like | TLR6 | " | |||
| Toll-like | TLR7 | " | resiquimod, imiquimod | ||
| Toll-like | TLR8 | " | |||
| Toll-like | TLR9 | " | CpG, DNA enriched in cytosine:guanosine pairs | ||
| Toll-like | TLR10 | " |