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Oxygen and the evolution of metabolic pathwaysWhile a considerable amount of evidence has been accumulated about the history of oxygen on this planet, little is known about the relative amounts to which primitive cells might have been exposed. One clue may be found in the metabolic pathways of extant microorganisms. While eucaryotes are principally aerobic organisms, a number are capable of anaerobic growth by fermentation. One such eucaryotic microorganism, Saccharomyces cerevisiae, will grow in the complete absence of oxygen when supplemented with unsaturated fatty acid and sterol. Oxygen-requiring enzymes are involved in the synthesis of both of these compounds. Studies have demonstrated that the oxidative desaturation of palmitic acid and the conversion of squalene to sterols occur in the range of 10-(3) to 10(-2) PAL. Thus, if the oxygen requirements of these enzymatic processes are an indication, eucaryotes might be more primitive than anticipated from the microfossil record. Results of studies on the oxygen requirements for sterol and unsaturated fatty acid synthesis in a more primitive procaryotic system are also discussed.
Document ID
Document Type
Conference Paper
Jahnke, L. L.
(NASA Ames Research Center Moffett Field, CA, United States)
Date Acquired
August 12, 2013
Publication Date
May 1, 1986
Publication Information
Publication: NASA, Washington Second Symposium on Chemical Evolution and the Origin and Evolution of Life
Subject Category
Space Biology
Accession Number
Distribution Limits
Work of the US Gov. Public Use Permitted.
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