title: An endogenous inhibitor of the protein tyrosine kinase activity of normal and malignant human lymphoid cells.
abstract: Tyrosine protein kinases (TPKs) have been implicated in mitotic signalling in a wide range of cells including lymphocytes. We describe here the partial characterization of a heat stable TPK inhibitor from both normal and malignant human lymphoid cells. Inhibitory activity was not attributable to contaminating ATPase, protease or phosphatase activities or to the Ca2+-binding protein S100. Preparations of the TPK inhibitor did not reduce the activity of cAMP-dependent protein kinase. While the inhibitor decreased the activity of TPKs towards an exogenous peptide substrate, it did not affect the autophosphorylation of microsomal TPKs. These results raise the possibility that the activity of TPKs in lymphoid cells may be regulated by an inhibitor protein.
authors.affiliation: Department of Haematology, Royal Free Hospital, London, UK.
authors.forename: B S
authors.initials: BS
authors.lastname: Hall
authors.forename: A V
authors.initials: AV
authors.lastname: Hoffbrand
authors.forename: R G
authors.initials: RG
authors.lastname: Wickremasinghe
mesh_terms: D000251:Adenosine Triphosphatases / Q000032:analysis; D017317:Annexin A6; D002135:Calcium-Binding Proteins / Q000032:analysis; D006358:Hot Temperature; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000378:metabolism*; D008214:Lymphocytes / Q000032:analysis*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors*
chemical_list: D017317:Annexin A6; D002135:Calcium-Binding Proteins; D011505:Protein-Tyrosine Kinases; D000251:Adenosine Triphosphatases