Alternative Pathway for Enzymatic Synthesis of Sphingomyelin

TABLE I Conversion of stearoyl-I -W-CoA to sphingonayelin The incubation mixtures in Part A contained 100 pmoles of potassium phosphate buffer, pH 7.8,80 mpmoles of stearoyl-I-‘4C-CoA (67,600 cpm), 2 pmoles of ATP, 2 rmoles of MgClz, and resuspended rat brain particulate preparations in a final volume of 1.18 ml. In Part B, the components of the mixtures were the same except that 1.0 ml of 100,000 X Q supernatant solution, obtained by treating the respective particulate fractions with sodium cholate, was employed. The mixtures were incubated under an atmosphere of Nz for 3 hours at 37’. At the end of the incubation period, 0.1 ml of methanol containing 1 mg of sphingomyelin (Wilson Laboratories, Experiment 1; Sylvania Company, Experiment 2) was added to each sample as carrier. The procedure for the recovery of the labeled sphingomyelin is described in the text. described by Sribney and Kennedy (1) and supported by the findings of Kopacsyk and Radin (12) in viuo or via the acylation of sphingosylphosphorylcholine.