SUBCELLULAR-LOCALIZATION OF DIACYLGLYCEROL KINASE-ACTIVITY IN STIMULATED AND UNSTIMULATED HUMAN PERIPHERAL-BLOOD LYMPHOCYTES AND NEUTROPHILS

The diacylglycerol (DAG) kinase activity was determined in crude cytos ol and membrane fractions in human peripheral blood lymphocytes and ne utrophils. In neutrophils the basal lipid kinase activity was indentic al in the two subcellular fractions whereas in lymphocytes the basal e nzyme activity was 1.6-fold higher in the membrane fraction. In genera l, the DAG kinase activity in lymphocyte fractions was 10- to 20-fold higher than in neutrophil fractions. When lymphocytes were stimulated with phytohaemagglutinin for 4 hours, a significant decrease in the DA G kinase activity in the membrane fraction was detected. By contrast, a 30-min activation with N-formyl-methionyl-leucyl-phenylalanine marke dly increased the lipid kinase activity in both subcellular fractions in neutrophils. This activity was partially inhibited by the compound R59022. These results suggest that the DAG kinase is widely distribute d in human leukocytes, but the enzyme's activity and regulation may va ry in different leukocyte types.