Linked cycles of oxidative decarboxylation of glyoxylate as protometabolic analogs of the citric acid cycle.
Greg Springsteen,Jayasudhan Reddy Yerabolu,Julia Nelson,Chandler Joel Rhea,Ramanarayanan Krishnamurthy +4 more
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TLDR
Two linked cycles of reactions that each oxidize glyoxylate into CO2 and generate intermediates shared with the modern TCA cycle are reported, shedding light into a plausible TCA protometabolism.Abstract:
The development of metabolic approaches towards understanding the origins of life, which have focused mainly on the citric acid (TCA) cycle, have languished-primarily due to a lack of experimentally demonstrable and sustainable cycle(s) of reactions. We show here the existence of a protometabolic analog of the TCA involving two linked cycles, which convert glyoxylate into CO2 and produce aspartic acid in the presence of ammonia. The reactions proceed from either pyruvate, oxaloacetate or malonate in the presence of glyoxylate as the carbon source and hydrogen peroxide as the oxidant under neutral aqueous conditions and at mild temperatures. The reaction pathway demonstrates turnover under controlled conditions. These results indicate that simpler versions of metabolic cycles could have emerged under potential prebiotic conditions, laying the foundation for the appearance of more sophisticated metabolic pathways once control by (polymeric) catalysts became available.read more
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Synthesis and breakdown of universal metabolic precursors promoted by iron
TL;DR: A purely chemical reaction network promoted by ferrous iron is described, in which aqueous pyruvate and glyoxylate build up 9 of the 11 intermediates of the biological Krebs (or tricarboxylic acid) cycle, including all 5 universal metabolic precursors.
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Nonenzymatic Metabolic Reactions and Life's Origins.
TL;DR: This review discusses metabolic pathways of relevance to the origin of life in a manner accessible to chemists, and summarizes experiments suggesting several pathways might have their roots in prebiotic chemistry.
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An appeal to magic? The discovery of a non-enzymatic metabolism and its role in the origins of life
TL;DR: It is discussed that, on the basis of non-enzymatic metabolism-like networks, one can elaborate stepwise scenarios for the origin of metabolic pathways, a situation that increasingly renders the origins of metabolism a tangible problem.
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A plausible metal-free ancestral analogue of the Krebs cycle composed entirely of α-ketoacids
R. Trent Stubbs,Mahipal Yadav,Ramanarayanan Krishnamurthy,Ramanarayanan Krishnamurthy,Greg Springsteen +4 more
TL;DR: It is shown that the reaction of glyoxylate with pyruvate under mild aqueous conditions produces a series of α-ketoacid analogues of the reductive citric acid cycle without the need for metals or enzyme catalysts.
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Modern views of ancient metabolic networks
Joshua E. Goldford,Daniel Segrè +1 more
TL;DR: This review highlights work that uses network-level approaches to shed light on key innovations in ancient life, including the emergence of proto-metabolic networks, collective autocatalysis and bioenergetics coupling.
References
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Hydrogen Peroxide on the Surface of Europa
Robert W. Carlson,Mark S. Anderson,Robert E. Johnson,William D. Smythe,Amanda R. Hendrix,Charles A. Barth,L. A. Soderblom,Gary B. Hansen,T. B. McCord,J. B. Dalton,Roger N. Clark,James H. Shirley,Adriana C. Ocampo,Dennis L. Matson +13 more
TL;DR: Spatially resolved infrared and ultraviolet wavelength spectra of Europa's leading, anti-jovian quadrant observed from the Galileo spacecraft show absorption features resulting from hydrogen peroxide, demonstrating that Europa's surface chemistry is dominated by radiolysis.
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The Implausibility of Metabolic Cycles on the Prebiotic Earth
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