CHARACTERIZATION OF THE PEST FAMILY PROTEIN-TYROSINE-PHOSPHATASE BDP1

Using a polymerase chain reaction (PCR) amplication strategy, we ident ified a novel protein tyrosine phosphatase (PTPase) designated Brain D erived Phosphatase (BDP1). The full length sequence encoded an open re ading frame of 459 amino acids with no transmembrane domain and had a calculated molecular weight of 50 kDa. The predicted amino acid sequen ce contained a PEST motif and accordingly, BDP1 shared the greatest ho mology with members of the PTP-PEST family. When transiently expressed in 293 cells BDP1 hydrolyzed p-Nitrophenylphosphate, confirming it as a functional protein tyrosine phosphatase. Northern blot analysis ind icated that BDP1 was expressed not only in brain, but also in colon an d several different tumor-derived cell lines. Furthermore, BDP1 was fo und to differentially dephosphorylate autophosphorylated tyrosine kina ses which are known to be overexpressed in tumor tissues.