Enzymatic reactions are decomposed into substrate-product pairs that link reactions within metabolic subnetworks.

<p>(<b>a</b>) An enzymatic reaction is broken down into pairwise relations between its substrates and products. These reactions are more complex than pairwise edges studied in most types of network analysis. Here, reactions are “hyper-edges”, meaning that the relations are between two sets of nodes instead of a pair of nodes. For an undirected reaction, one can consider both directions when breaking the reaction into substrate-product pairs. (<b>b</b>) A subnetwork is composed of a set of reactions. In the model, different subnetworks can potentially share reactions and therefore have overlapping regions.