Receptor tyrosine kinase required for neurogenesis in the developing central nervous system (PubMed:23667670). Following activation by alkal ligands (alkal1, alkal2a or alkal2b) at the cell surface, transduces an extracellular signal into an intracellular response (PubMed:29078341). Ligand-binding to the extracellular domain induces tyrosine kinase activation, resulting in the activation of the mitogen-activated protein kinase (MAPK) pathway (PubMed:23667670). Phosphorylates almost exclusively at the first tyrosine of the Y-x-x-x-Y-Y motif (By similarity). ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] Inhibited by ALK inhibitor TAE684. Homodimer; homodimerizes upon binding to alkal ligands (alkal1, alkal2a or alkal2b). Highly expressed in the developing central nervous system: highly expressed in brain, with much lower expression in heart, caudal fin and testis. First detected at 12 hours post-fertilization (hpf), during the initiation of segmentation and neurulation (PubMed:23667670). Expression increases with the most profound increase at 48 hpf (PubMed:23667670). Morpholino knockdown of the protein causes impaired neuronal differentiation and reduced neuron numbers in the hindbrain (PubMed:23667670). Fishes display normal iridophore development (PubMed:29078341). Belongs to the protein kinase superfamily. Tyr protein kinase family. Insulin receptor subfamily.