Glucose Phosphate Hydrolysis in Aged Nanomolar Inorganic Iron(III) Salt Solution: An Inorganic Enzyme? (2008, Proof, Unpublished)

Note on the Historical Context of This Submission This work was originally conducted in 2008 but was not published at the time due to limited recognition of non-biological phosphate turnover mechanisms. In the years since, growing evidence has accumulated for abiotic phosphatase-like activity in minerals, inorganic complexes, and iron-based nanoparticles. These findings have renewed relevance to current discussions in geochemistry, catalysis, and the origin of life. In light of this, we are releasing the original manuscript for open access and scholarly evaluation through ChemRxiv. The following was the abstract ( unchanged) Sugar phosphate hydrolysis is one of the most important chemical processes in biological systems and is catalyzed by enzymes such as purple acid phosphatase (PAP). Different sources of PAPs with various sequences and polypeptide chains have a common characteristic of Fe–Fe or Fe–metal with a μ-(hydr)oxo ligand bridging in a consequence that coordinates with seven invariant amino acids. In biomimetics, different metal complexes, including diiron complexes, with the function of PAP have been synthesized based on the μ-(hydr)oxo metal bridge structure. Here we report that aged nanomolar inorganic iron(III) salt solutions can significantly promote the hydrolysis of glucose-6-phosphate with enzyme-like, pseudo-first-order reaction kinetics. The catalytic activity increases with the aging time of the nanomolar iron solution. The formation of diiron or polyiron with the μ-(hydr)oxo bridge through acid forced hydrolysis of iron(III) salt during the aging process may contribute to the observed catalytic activity. The turnover number (kcat) of the catalyst is possibly the same order of magnitude as natural PAP. We demonstrate for the first time that these aged iron solutions, without adding any organic ligands, perform the same function of enzymes (natural and biomimetics) and might serve as an inorganic enzyme. This discovery is not only important for phosphorus metabolism, but also for the nature and evolution of enzymes. We believe this inorganic enzyme is one of many ubiquitous sets of enzyme undiscovered in nature which act as a bridge between the inorganic and organic worlds and play a critical role in the emergence of life.