Water is the medium of life and a key compound produced and/or consumed during organic and inorganic catabolism and anabolism of molecules. Water comprises 99.4% of metabolites in Escherichia coli and serves as a recurring reaction substrate, intermediate, cofactor, and product. The authors calculated a lower limit for extent of participation of water molecules in chemical transformation during replication of a single Escherichia coli. Specifically, the quantity of water transformed under oxic conditions during protein synthesis and oxidative phosphorylation were studied because they are dominant metabolic hubs. Water molecules involved in changes in metal coordination and in synthesis of RNA, DNA, and membrane lipids were not included in this analysis. The results showed that about 88% of water molecules in an E. coli cell participate chemically in reactions of amino acid biosynthesis and polymerization. In oxidative phosphorylation, about 278% of the total water molecules participated, suggesting that an average water molecule is repeatedly used and transformed. Thus, overall it was calculated that during replication of a single E. coli, an average water molecule is chemically transformed or mechanistically involved in catalysis as least 3.7 times. A survey here indicated that there are more biochemical reactions containing water as a substrate or a product than reactions consuming or producing ATP or NAD+. The data demonstrates the importance of water chemistry and supports a model of water as the reactive nexus of biology. Understanding water as both a chemical participant and a medium can provide insight into the origins of life.
A story highlighting this paper has been published on NewScientist: https://www.newscientist.com/article/mg24933184-400-water-may-be-even-more-crucial-to-life-than-we-thought/
Frenkel-Pinter, M., Rajaei, V., Glass, J.B. et al. Water and Life: The Medium is the Message. J Mol Evol (2021). https://doi.org/10.1007/s00239-020-09978-6