Acute myeloblastic leukemia with active tyrosine protein kinase

High level of tyrosine protein kinase activity was found in a membrane fraction isolated from an acute myeloblastic leukemia, out of 24 leukemias of different origin investigated. The major substrate for tyrosine phosphorylation in vitro was a 58 kDA protein (p58). The phosphorylation proceeded actively at 0 degrees C and was strongly stimulated by Mn2+ ions. Comparison by partial proteolysis of the p58 with similar phosphoproteins from a T-lymphoma line (KE37) and from lectin stimulated lymphocytes showed high similarity. The possible role of the tyrosine kinase activity in this leukemia is discussed.