Porphyrin in Prebiotic Catalysis: Ascertaining a Route for the Emergence of Early Metalloporphyrins^**

Graphical Abstract

Putative pathway for the emergence of primitive metalloporphyrins: We studied the influence of the porphyrin scaffold tetraphenylporphyrin tetrasulfonic acid (TPPS), on the modulation of metal ion-mediated oxidation. We show that TPPS can modulate metal ion oxidizing activity by forming metal-coordinated complexes or non-coordinated aggregates. We also show the formation of metal-TPPS coordinated complexes under prebiotic settings, highlighting their potential role as primitive catalysts.

Abstract

Metal ions are known to catalyze certain prebiotic reactions. However, the transition from metal ions to extant metalloenzymes remains unclear. Porphyrins are found ubiquitously in the catalytic core of many ancient metalloenzymes. In this study, we evaluated the influence of porphyrin-based organic scaffold, on the catalysis, emergence and putative molecular evolution of prebiotic metalloporphyrins. We studied the effect of porphyrins on the transition metal ion-mediated oxidation of hydroquinone (HQ). We report a change in the catalytic activity of the metal ions in the presence of porphyrin. This was observed to be facilitated by the coordination between metal ions and porphyrins or by the formation of non-coordinated complexes. The metal-porphyrin complexes also oxidized NADH, underscoring its versatility at oxidizing more than one substrate. Our study highlights the selective advantage that some of the metal ions would have had in the presence of porphyrin, underscoring their role in shaping the evolution of protometalloenzymes.