Before revision:  In this paper we evaluate different network representations of metabolism and describe their structure with respect to both modularity and currency metabolites .
After revision:  In this paper we evaluate different network representations of metabolism , applied to data from URLanisms and databases. The graph representations are evaluated by comparing the overlap between clusters (network modules) and annotated functions, and also by comparing the set of identified currency metabolites with those that other authors have identified using qualitative biological arguments .