Two different examples of additional gene-reaction associations for genes already present in the Oliveira network. (A) Differences in cofactor usage: two predicted gene-reaction associations involving a single L. lactis gene (zwf), differing on the level of cofactor (i.e. NAD versus NADP). Abbreviations: g6p = D-Glucose 6-phosphate and 6pgl = 6-phospho-D-glucono-1,5-lactone (B) Differences in substrate utilization: additional gene-reaction associations were predicted for sdaA and ilvA, with similar biochemistry but different amino acids as substrate. Note that some of the additional associations involve reactions already associated to other genes (31% of all additional associations). Abbreviations: ser-L = L-Serine, pyr = Pyruvate, thr-L = L-Threonine, 2obut = 2-Oxobutanoate and ser-D = D-Serine.