– 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. May also have serine/threonine protein kinase activity. Required for longitudinal bone growth through regulation of chondrocyte differentiation. May be indirectly involved in protein transport from the Golgi apparatus to the plasma membrane. Probably plays a role in platelets: rapidly and quantitatively secreted from platelets in response to stimulation of platelet degranulation.