Effects of 1-palmitoyl-sn-glycero-3-phosphorylcholine on mouse liver microsomal sialyltransferase

1. Mouse liver microsomal sialyltransferase is strongly inhibited by 1-palmitoyl-sn-glyccro-3-phosphoryleholine. 2. The inhibiting ability is approximately the same whatever the enzyme form may be, microsomal or solubilized. 3. The microsomal enzyme requires neither Mn2+ ions nor exogenous glycoproteinic acceptor for maximal catalytic activity. 4. The lysophospholipid acts as a non-competitive or a mixed-type inhibitor whether the enzyme is respectively microsomal or solubilized. 5. The lysophospholipid and the colchicine prove additive effects in inhibiting the microsomal sialyl-transferase.