Figure 5.

Overview of the SMS reaction steps. In step (1), one of the PC molecules was highlighted. In step (2), the PC at the binding site of the SMS enzyme is observed. The transfer of the phosphocholine head to the tyrosine of the enzyme forms a modified tyrosine shown in magenta in step 3. The removal of the phosphocholine head from the PC generates DAG (3). Thus, it is free to move through the membrane (4). In steps 5 and 6, ceramide moves from the membrane (5) to the SMS (6). The transfer of the phosphocholine head from the modified tyrosine to Cer generates SM (7), followed by its release into the membrane (8).