Fixation of carbon dioxide by extracts of the strict autotroph Thiobacillus denitrificans

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Abstract
Extracts of the strict chemoautotroph, T. denitrificans, fixed C14O2 into the carboxyl group of 3-phosphoglycerate in the presence of either ribose 5-phosphate plus adenosine triphosphate, (ATP) or ribulose 1:5-diphosphate alone. The extracts contained phosphoglycerokinase, triose phosphate dehy-drogenase, aldolase and hexose diphosphatase, and synthesized hexose phosphates from phosphoglycerate, ATP and reduced diphosphopyridine nucleotide. Ribose 5-phosphate was rapidly metabolized in the absence of ATP with the formation of triose phosphate, hexose monophosphate and 2 compounds which behaved chromatographically as heptulose and tetrose phosphates. The extracts converted hexose diphosphate into a mixture of pentose, heptulose and tetrose phosphates. Hexose monophosphate isomerase and enolase were also present in the extracts. It is concluded that T. denitrificans can synthesize hexose phosphates from CO2 by a cyclic mechanism similar to that found in green plants.