The function of ACP4 (acid phosphatase 4, Ensembl gene identifier ENSG00000142513) is as follows. Protein tyrosine phosphatase that dephosphorylates the receptor tyrosine-protein kinase ERBB4, thereby inhibiting its ligand- induced proteolytic cleavage (PubMed:15219672). Involved in odontogenesis (PubMed:27843125). Regulates odontoblast cell fate via its extracellular catalytic domain by inhibiting proliferation and promoting differentiation (By similarity). {ECO:0000250|UniProtKB:D3YTS9, ECO:0000269|PubMed:15219672, ECO:0000269|PubMed:27843125}.