The Effect of Phytohemagglutinin on the Activity of PC-cytidyl Transferase and PC-glyceride Transferase in Cultured Porcine Lymphocytes

Abstract

Lymphocytes from the mesenteric lymph nodes of pigs were cultured for 61 h with and without phytohemagglutinin (PHA). Every 12 h the activity of PC-cytidyl transferase (CTP: cholinephosphate cytidylyltransferase, EC 2.7.7.15) and PC-glyceride transferase (CDPcholine: 1,2-diglyceride cholinephosphotransferase, EC 2.7.8.2) was correlated with the incorporation of Me-14C-choline into total lipid. Maximum labelling of total lipid ([Formula: see text] of the label was incorporated into lecithin) occurred between 37 and 48 h of culture. The activity of PC-cytidyl transferase was stimulated up to 10-fold at 37 h while the activity of PC-glyceride transferase exhibited a maximal sixfold increase at 48 h. Addition of actinomycin D (0.10 μg/ml) or cycloheximide (1.0 μg/ml) inhibited simultaneously the induction of the activity of both enzymes and the increased incorporation of 14C-choline into total lipid. It is postulated that the accelerated production of lecithin in PHA-stimulated lymphocytes is dependent on the increased synthesis and/or activity of both these enzymes.