Secreted tyrosine-protein kinase that mediates phosphorylation of extracellular proteins and endogenous proteins in the secretory pathway, which is essential for patterning at organogenesis stages. Mediates phosphorylation of MMP1, MMP13, MMP14, MMP19 and ERP29 (PubMed:25171405). May also have serine/threonine protein kinase activity (PubMed:25171405). Required for longitudinal bone growth through regulation of chondrocyte differentiation (PubMed:19097194, PubMed:23792766). May be indirectly involved in protein transport from the Golgi apparatus to the plasma membrane (PubMed:19465597). Probably plays a role in platelets: rapidly and quantitatively secreted from platelets in response to stimulation of platelet degranulation (PubMed:25171405). ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] Both secreted and present in the Golgi apparatus. Strongly expressed in adult heart, liver and testis with weak expression in brain, spleen, lung and thymus. In the humerus, strongly expressed in early flat proliferative chondrocytes. In the embryo, expressed in the anterior visceral endoderm and anterior primitive streak at 6.5 dpc. At 7.5 dpc, expressed in the anterior definitive endoderm (ADE) and anterior mesoderm but not in the notochord. At 8.0 dpc, expressed in the ADE and anterior embryonic mesoderm. At 8.5 dpc, expressed more broadly in anterior tissues and at the midline of the neural plate in the midbrain region as well as the lateral margins of the neural plate posterior to the metencephalic region. Also weakly expressed in the anterior mesenchyme. At 9.5 dpc, strongest expression in branchial arches and limb buds. During mid-gestation, expression continues in mesenchymal cells, particularly in areas where these cells condense. Expressed throughout embryogenesis and in adulthood. During embryogenesis, expression is high at transition phases of mesenchymal cell differentiation such as from mesenchymal cells to chondrocytes and from mesenchymal to mesothelial cells. Expressed throughout all stages of humerus bone formation. During lung development, expressed in all mesenchymal cells at the early pseudoglandular stage. Expression is rapidly lost from the mesenchyme of the lung interstitium during the mid-to-late pseudoglandular stage but continues throughout life in the mesothelial pleural cells. Down-regulated by hedgehog (Hh) signaling. Phosphorylated on tyrosines; probably via autophosphorylation. N-glycosylated. Morphological defects at birth including growth retardation, short limbs, cleft palate, sternal dysraphia, shortened intestine and cyanosis. Long bones display reduced mineralization due to delayed chondrocyte differentiation. Neonates breathe abnormally, do not suckle and die within a day after birth, probably due to insufficient respiration as a result of the cleft palate. Belongs to the protein kinase superfamily.