Biochemical subnetworks identified by the GGM. Line widths correspond to partial correlation coefficients. A: Elongation and desaturation signatures, most likely mediated by ELOVL6 and SCD, for C16 and C18 fatty acids incorporated in lyso-PCs and sphingomyelins. B: Top: Diacyl-phosphatidylcholine (PC aa) species with elongation and peroxisomal β-oxidation associations. Several combinatorial variants of side chain compositions are possible for C36:4 and C38:4, and thus different enzymes could mediate this connection. Bottom: Alkyl-acyl-phosphatidylcholines (PC ae) with supposedly distinct side chain composition, giving rise to a low association with a directly connected species (C36:2). C: Recovered β-oxidation pathway from C18 down to C4. Four enzymes with overlapping substrate specificities catalyze the rate-limiting reactions of this pathway. D: Two high-scoring triads, where metabolite pairs with a pathway distance of two constitute strong partial correlations. This feature of partial correlations aids in the reconstruction of the network topology beyond the direct neighborhood of each metabolite.
Krumsiek et al. BMC Systems Biology 2011 5:21 doi:10.1186/1752-0509-5-21