It is known that the importance of phosphate synthesis, as the authors stated. However, how these phosphorus compounds become the small molecular to be used, including the hydrolysis of ATP, or polyphosphate, as the energy source of life?

My work indicated that iron oxide nanoparticles in solution can plan significant role, their catalysis behavior are similar to the natural enzyme with the enzyme kinetics. The nanoparticles with the oxo-Fe structure, similar to the metal center of natural phosphatase (e.g., purple acid phosphatase, PAP), might contribute to the observed catalytic activity. They are sensitive to the temperature, pH and the medium in the environment. This observation, along with recent findings on iron oxide as peroxidase (Chaudhari et al. 2012; Chen et al. 2012; Gao et al. 2007; Peng et al. 2011), vanadium pentoxide as bromoperoxidase (André et al. 2011), and molybdenum trioxide nanoparticles as sulfite oxidase (Ragg et al. 2014) further support the concept of inorganic enzymes (Huang and Zhang, 2012, Huang, 2017). The catalytic characteristics in these nanoparticles might be due to the structure of metal oxides or metal bond in the oxides, i.e., not merely the simple surface area of the nanoparticles. Furthermore, all the enzyme-like oxide nanoparticles are composed from the transition metals, with the oxo bond acting either as the terminal ligand or as a bridge. These results provide solid evidence that biocatalysts can be formed and function before the protein and RNA world and thereby offer a solution to the “chicken and egg” at life’s beginnings (Cairns-Smith 1985; Cairns-Smith 2008).