Autotrophic Carbon Fixation in Biology Pathways, Rules, and Speculations

Autotrophic Carbon Fixation in Biology Pathways, Rules, and Speculations 

Ivan A. Berg, Daniel Kockelkorn, W. Hugo Ramos-Vera, Rafael Say, Jan Zarzycki, and Georg Fuchs 

In general terms, the endergonic assimilation of C02 into cellular building blocks requires reducing equivalents and an input of energy. It can be formulated as  

Carbon Dioxide as Chemical Feedstock. Edited by Michele Aresta Copyright 2010 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 978-3-527-32475-0 

The question is therefore, what are the principal requirements of an autotrophic carbon-fixation mechanism An organic molecule serves as a C02 acceptor molecule, which becomes carboxylated by a carboxylase enzyme. This C02 acceptor molecule needs to be regenerated in a reductive autocatalytic cycle. The product that can be drained off from such a metabolic cycle should be a central cellular metabolite, from which all cellular building blocks for polymers can be derived examples of such central metabolites are acetyl-CoA, pyruvate, oxaloacetate, 2-oxoghitarate, phosphoe-nolpyruvate, and 3-phosphoglycerate. Importantly, the intermediates should not be toxic to the cell. The irreversible steps of the pathway are driven by ATP hydrolysis, while the reduction steps are driven by low-potential reduced coenzymes. 

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