Primary Metabolic Chemistry.
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
Thioesters and acyl phosphates are important metabolites throughout the biosphere. This may imply that they were involved in prebiotic chemistry. The study of the reactivity of thioesters and acyl phosphates may therefore provide some insights into the possible roles for these molecules in prebiotic chemistry. The work described in this thesis demonstrates that acetyl phosphate and inorganic phosphate react to form pyrophosphate in the presence of salts of some divalent metals. Divalent metal ions and nitrogen containing compounds act in synergy to promote pyrophosphate formation in some cases. Ferrous salts were much more efficient at promoting the formation of pyrophosphate than similar reactions containing magnesium ions, Addition of pyridine, or a variety of other nitrogen containing compounds, did not enhance the pyrophosphate yield. The promotion of pyrophosphate formation at near neutral pH by ubiquitous metal salts is considered to be a feasible route for prebiotic production of pyrophosphate. One chemoautotrophic origin of life theory concentrates on the oxidative formation of pyrite (FeS2) from ferrous sulfide and hydrogen as a possible source of prebiotic reductive power. N-Phenyl acetamide can be prepared from mercaptoacetic acid and aniline in water using FeS/H2S as a reagent system. We have established that one possible intermediate, N-phenyl mercaptoacetamide does react to give the product, and that this reaction is fast. Ferrous ions were observed to promote the formation of N-acetyl alanine from alanine and thioacetic acid. Zinc and cadmium ions on the other hand, promote the hydrolysis of thioacetic acid to acetic acid in preference to the N-acylation reaction. Both ferrous ions and ferro cyanide ions were observed to promote the peptide bond formation between protected amino acid derivatives. The results described in this thesis are consistent with the proposal that iron chemistry may have been important in prebiotic chemistry.