Category II solution for blocked reactions in peroxisomal fatty acid degradation. The blocked reactions (red arrows) are all catalysed by acetyl-CoA-acyltransferase (EC 184.108.40.206). The SMILEY solutions (green arrows) for each of the five blocked reactions generated a complete degradation pathway for saturated fatty acids in the peroxisome starting with stearoyl-CoA (StCoa) and ending in octanoyl-CoA (OcCoa) through stepwise removal of two carbons from the acyl chain. Abbreviations are as described in the BiGG database . Enzyme commission numbers of all reactions are shown. Metabolites and reactions in blue are not blocked. The number of carbons of each fatty acid-CoA derivative is indicated. The results show that the SMILEY algorithm is capable of generating plausible solutions to blocked reactions in human metabolism. The resolving reactions suggested by SMILEY correspond to well-characterised reactions involved in the β-oxidation of fatty acids [50, 79].