Results of these evolutionary simulations show that under such a selective pressure, mutational processes easily lead to the emergence of pathways with two separate sub-pathways (i.e. modules) each mediating a distinct response only to one of the signals.
Similarly, employing a high fitness cost for additional proteins in the model prohibits pathway growth and emergence of modularity (see Methods).
Thus, the emergence of metabolic pathways allowed primitive organisms to become increasingly less dependent on exogenous sources of organic compounds.
It facilitates the appearance of drug resistance in microorganisms, as well as the emergence of bioremediation pathways for anthropogenic toxins.
The key characteristic of the kinetics model in Scheme 1 is the emergence of branched pathways from the initial encounter complex, having Michaelis states of differing reactivity.
The emergence of biochemical pathways that produce and then utilize ketone bodies is believed to be a major selective force in the evolutionary history of Homo sapiens and this adaptive process, along with others, enables human adults to survive for more than two months without food intake [ 1].
This drove a number of adaptations, among which the emergence of the phenylpropanoid pathway was crucial, leading to essential compounds such as flavonoids and lignin.
These have been likely recruited from preexisting enzymes in parallel to the emergence of the sterol pathway in the lineage leading to the LECA.
The emergence of publicly available pathway databases has provided biologists excellent resources to attain a deeper understanding of biological mechanisms by providing organization to a large list of differentially expressed genes and proteins.
