Figure 1. Did metal-based catalysis facilitate the formation of the first metabolic enzymes?

(a) A precursor of glycolysis and the PPP was catalysed by ferrous iron and other metals found in the prebiotic oceans. (b) RNA molecules (and/or peptides?) bound the metal ions and in that way increased their accessibility and potentially their local concentration. (c) Positive selection of more sophisticated structures achieved specificity by preventing contact of the metal catalyst with some of the metabolites, and increasing the affinity for others.