title: Phosphotyrosine phosphatase activity in human platelets.
abstract: Using O-phosphotyrosine as a substrate, human platelets were shown to contain a highly active phosphotyrosine phosphatase (PTPase) activity. This activity was potently inhibited by vanadate, molybdate, and HgCl2. About 80% of the PTPase activity was particulate. When Triton-solubilized PTPase activity from whole platelets was applied to a DEAE Sephacel column about 40% came through unbound. The activity that bound was eluted by a NaCl gradient as a broad, heterogeneous peak. The possibility is raised for the existence of multiple forms of phosphotyrosine phosphatases in human platelets. That one or more of these forms may be regulated by activators of platelet aggregation and secretion, such as thrombin and collagen, is discussed.
authors.affiliation: Department of Pharmacology, University of Connecticut Health Center, Farmington 06030.
authors.forename: H M
authors.initials: HM
authors.lastname: Smilowitz
authors.forename: L
authors.initials: L
authors.lastname: Aramli
authors.forename: D
authors.initials: D
authors.lastname: Xu
authors.forename: P M
authors.initials: PM
authors.lastname: Epstein
mesh_terms: D001792:Blood Platelets / Q000201:enzymology*; D002848:Chromatography, DEAE-Cellulose; D003094:Collagen / Q000378:metabolism; D006801:Humans; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000097:blood*; D017027:Protein Tyrosine Phosphatases; D012969:Sodium Fluoride / Q000494:pharmacology; D013431:Sulfates / Q000494:pharmacology; D013917:Thrombin / Q000378:metabolism; D014638:Vanadates / Q000494:pharmacology; D015032:Zinc / Q000494:pharmacology; D019287:Zinc Sulfate
chemical_list: D013431:Sulfates; D014638:Vanadates; D019287:Zinc Sulfate; D012969:Sodium Fluoride; D003094:Collagen; D010749:Phosphoprotein Phosphatases; D017027:Protein Tyrosine Phosphatases; D013917:Thrombin; D015032:Zinc