Table 3. Steady-state total mass of complex sphingolipid sub-populations in SL-E model under different experimental conditions, after 60 minutes.

	IPC	MIPC	M(IP)2C	CS
	X 8, X 20	X 18, X 21	X 19, X 22	X 8, X 18, X 19, X 20, X 21, X 22
Wild Type (mol%)	1.02	1.40	0.085	2.505
1% SPT	0.34	0.68	0.57	0.54
1% SPT (120 min)	0.08	0.49	0.54	0.32
1% IPC synthase	0.35	0.66	0.63	0.53
12.5% Ceramide synthase	0.83	0.92	0.94	0.89

Wild type condition is represented by the sum of the basal values; the other experimental conditions correspond to fold changes with respect to the wild type after decreasing the specific activity of serine palmitoyl transferase (X ₁₅₇), IPC synthase (X ₁₃₃), and ceramide synthase (X ₁₃₄) to 1% or 12.5%. Complex sphingolipids: IPC in Golgi compartment plus plasma membrane (X ₈+X ₂₀), MIPC in Golgi compartment plus plasma membrane (X ₁₈+X ₂₁), M(IP)₂C in Golgi compartment plus plasma membrane (X ₁₉+X ₂₂). CS represents the total of complex sphingolipids.