Porphyrin in prebiotic catalysis: Ascertaining a route for the emergence of early metalloporphyrins

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 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.

Modeling prebiotic catalysis with nucleic acid-like polymers and its implications for the proposed RNA world

The theory that RNA molecules played a pivotal role in the early evolution of life is now widely accepted. Studies related to this hypothetical “RNA world” include three major areas: the formation of precursors for the first RNA molecules, the polymerization process, and the potential of RNA to catalyze chemical and biochemical reactions. Several chemical and biochemical studies performed under simulated prebiotic conditions support the role of RNA as both genetic as well as catalytic material. However, owing to the lack of credible mechanism for de novo nucleic acid synthesis and the hydrolytic instability of RNA molecules, there has been some serious discussion of whether biopolymers that closely resembled nucleic acid preceded the “RNA world”. In this context, an overview of prebiotic chemistry, the role of mineral surface, and the significance of studies related to RNA-like polymers in the origin of life are presented here.