Pseudokinase that acts as an allosteric activator of the Golgi serine/threonine protein kinase FAM20C and is involved in biomineralization of teeth. Forms a complex with FAM20C and increases the ability of FAM20C to phosphorylate the proteins that form the 'matrix' that guides the deposition of the enamel minerals. . This is the function of FAM20A (FAM20A golgi associated secretory pathway pseudokinase, Ensembl gene identifier ENSG00000108950).