Enables protein tyrosine kinase binding activity. Involved in regulation of calcium ion transmembrane transport and regulation of peptidyl-tyrosine phosphorylation. Located in cytoplasm. Used to study type 1 diabetes mellitus. Human ortholog(s) of this gene implicated in several diseases, including Addison's disease; Meniere's disease; autoimmune disease (multiple); chronic lymphocytic leukemia; and pulmonary tuberculosis. Orthologous to human PTPN22 (protein tyrosine phosphatase non-receptor type 22). [provided by Alliance of Genome Resources, Apr 2022]