A non-specific tyrosine phosphatase that dephosphorylates a diverse number of substrates under acidic conditions (pH 4-6) including alkyl, aryl, and acyl orthophosphate monoesters and phosphorylated proteins (PubMed:10506173, PubMed:15280042, PubMed:20498373, PubMed:9584846). Has lipid phosphatase activity and inactivates lysophosphatidic acid in seminal plasma (PubMed:10506173, PubMed:15280042). Tyrosine phosphatase that acts as a tumor suppressor of prostate cancer through dephosphorylation of ERBB2 and deactivation of MAPK-mediated signaling (PubMed:20498373). In addition to its tyrosine phosphatase activity has ecto-5'-nucleotidase activity in dorsal root ganglion (DRG) neurons. Generates adenosine from AMP which acts as a pain suppressor (By similarity). (Microbial infection) Forms amyloid beta-sheet fibrils in semen. These fibrils, termed SEVI (semen-derived enhancer of viral infection) capture HIV virions, attach them to target cells and enhance infection (PubMed:18083097, PubMed:19451623, PubMed:19897482). SEVI amyloid fibrils are degraded by polyphenol epigallocatechin-3-gallate (EGCG), a constituent of green tea (PubMed:19451623). Target cell attachment and enhancement of HIV infection is inhibited by surfen (PubMed:19897482). Also similarly boosts XMRV (xenotropic murine leukemia virus-related virus) infection (PubMed:19403677). a phosphate monoester + H2O = an alcohol + phosphate 1-(9Z-octadecenoyl)-sn-glycero-3-phosphate + H2O = 1-(9Z-octadecenoyl)-sn-glycerol + phosphate a ribonucleoside 5'-phosphate + H2O = a ribonucleoside + phosphate H2O + O-phospho-L-tyrosyl-[protein] = L-tyrosyl-[protein] + phosphate Phosphatase activity inhibited by L(+)-tartrate, and by its derivative, alpha-benzylaminobenzylphosphonic acid. Homodimer; dimer formation is required for phosphatase activity. Appears to shuttle between the cell membrane and intracellular vesicles. Colocalizes with FLOT1 at cell membrane and in intracellular vesicles (PubMed:17638863). Colocalizes with LAMP2 on the lysosome membrane (PubMed:17897319). Highly expressed in the prostate, restricted to glandular and ductal epithelial cells. Also expressed in bladder, kidney, pancreas, lung, cervix, testis and ovary. Weak expression in a subset of pancreatic islet cells, squamous epithelia, the pilosebaceous unit, colonic neuroendocrine cells and skin adnexal structures. Low expression in prostate carcinoma cells and tissues. Widely expressed. Expressed in the sarcolemma of skeletal muscle. N-glycosylated. High mannose content, partially sialylated and fucosylated biantennary complex. Also fucosylated with partially sialylated triantennary complex oligosaccharides. Proteolytically cleaved in seminal fluid to produce several peptides. Peptide PAPf39, the most prominent, forms amyloid beta-sheet fibrils, SEVI (semen-derived enhancer of viral infection). Has been used as a diagnostic tool for staging metastatic prostatic cancer. Belongs to the histidine acid phosphatase family.