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. Interacts with FAM20C; probably forming a heterotetramer of 2 subunits of FAM20A and 2 subunits of FAM20C. Highly expressed in lung and liver. Intermediate levels in thymus and ovary. N-glycosylated. The disease is caused by variants affecting the gene represented in this entry. Belongs to the FAM20 family. Although strongly related to other members of the family, lacks the kinase activity. A conserved Asp/Glu residue present in other members of the family, which coordinates the Mn(2+) ion and the ion-pair Lys and is indispensable for kinase activity, is replaced by a Gln in position 258.