Reversibility in enzymes belonging to central carbon metabolism endows an evolutionary fitness in enabling ability to grow on different substrates

Many enzymes in central carbon metabolism are reversible. Thus, substrates could be reversibly converted to product and back. Little is known about why evolution accompanied by natural selection has afforded such capability to biological systems. One possibility is that reversibility in enzymes of central carbon metabolism affords multiple entry points (i.e., intermediates) for different substrates to plug into the cell’s metabolic network, which is essential to potentiate cell growth. Doing it this way allows the cell to grow on a larger variety of substates, which meant that the fitness of the organism in different environments is improved. Specifically, less often used substrates could be converted to intermediates in central carbon metabolism in one or two steps. Once connected to central carbon metabolism, the intermediate could move up or down the metabolic pathway through enzyme reversibility, and in the process generates the building blocks needed to synthesize other essential intermediates for the cell. Hence, less often used substrates could be employed to support cell growth, which endows an evolutionary advantage to the species. Overall, while the reasons underpinning enzyme reversibility in central carbon metabolism remains to be understood, the hypothesis that posits reversibility as a method by which different entry points to central carbon metabolism could be opened to different substrates is intriguing. In this schema, less often used substrates could be plugged into central carbon metabolism through an intermediate. Once plugged in, enzyme reversibility would allow the metabolic flux to move up and down the metabolic pathway, thereby, allowing substrates intermediates to be generated for supporting the synthesis of essential cellular building blocks and biomass.