[M-IS07] Astrobiology

[MIS07-08] Synthesis of hexose phosphate for non-enzymatic glycolysis and pentose phosphate pathway on early Earth

*Yuta Hirakawa¹, Takeshi Kakegawa¹, Yoshihiro Furukawa¹ (1.Tohoku University)

Keywords:Hexose, phosphate, glycolysis, pentose phosphate pathway

Glycolysis and pentose phosphate pathway play essential roles in modern cells to supply various biomolecules and their precursors. These reactions are presumed to be one of the most ancient metabolic pathways. Several previous studies have investigated non-enzymatic glycolysis and pentose phosphate pathway and showed that a part of these metabolism-like reactions progressed from glucose 6-phosphate and 6-phosphogluconate under the prebiotically plausible condition. Such non-enzymatic metabolism-like reactions might have been inherited by biological reactions. However, it remains unclear how these phosphorylated molecules and their precursors (i.e., glucose and gluconate) were provided on the early Earth. Here, we show the formation of glucose and gluconate from simple aldehydes via a formose-like reaction in an alkaline solution and further show the regioselective phosphorylation of these compounds with the help of borate and urea. An aqueous solution containing formaldehyde and glycolaldehyde was heated in the presence of Ca(OH)₂ at 95°C for 72 hours. The experimental solution was analyzed with GC-MS for sugar analysis and LC-MS/MS for gluconate analysis. For the phosphorylation experiments, aqueous solutions containing Na₂HPO₄ and glucose or gluconate were dried in the presence of boric acid and urea at 80°C for 24 hours. The dried residue was dissolved in H₂O, followed by LC-MS/MS analysis. GC-MS analysis revealed the formation of glucose and several hexoses. LC-MS/MS analysis of the formose-like reaction products showed the formation of a mixture of sugar acids, including gluconate. The product analysis of the phosphorylation experiment revealed the formation of glucose 6-phosphate and 6-phosphogluconate. The borate-added samples showed higher yields of phosphorylated compounds than the samples with borate. These results suggest that the starting molecules of the non-enzymatic glycolysis-like and pentose phosphate pathway-like reactions were provided through formose-like reaction in borate-rich evaporitic environments on early Earth, which implies that the non-enzymatic metabolism-like reactions provided various biomolecules and their precursors on early Earth.