  The architecture of biological networks has been reported to exhibit high
level of modularity, and to some extent, topological modules of networks
overlap with known functional modules. However, how the modular topology of the
molecular network affects the evolution of its member proteins remains unclear.
In this work, the functional and evolutionary modularity of Homo sapiens (H.
sapiens) metabolic network were investigated from a topological point of view.
Network decomposition shows that the metabolic network is organized in a highly
modular core-periphery way, in which the core modules are tightly linked
together and perform basic metabolism functions, whereas the periphery modules
only interact with few modules and accomplish relatively independent and
specialized functions. Moreover, over half of the modules exhibit
co-evolutionary feature and belong to specific evolutionary ages. Peripheral
modules tend to evolve more cohesively and faster than core modules do. The
correlation between functional, evolutionary and topological modularity
suggests that the evolutionary history and functional requirements of metabolic
systems have been imprinted in the architecture of metabolic networks. Such
systems level analysis could demonstrate how the evolution of genes may be
placed in a genome-scale network context, giving a novel perspective on
molecular evolution.
