A novel receptor-type protein tyrosine phosphatase (RPTP) protein or glycoprotein and the DNA coding therefor is expressed in a wide variety of mammalian tissues. Included in this family of proteins are human RPTPα, human RPTPβ and human RPTPγ. The RPTP protein or glycoprotein may be produced by recombinant means. Antibodies to the proteins, methods for measuring the quantity of the proteins, methods for screening compounds, such as drugs, which can bind to the proteins and inhibit or stimulate their activity, are provided.