Biographical Memoirs Volume 84 (2004) / Chapter Skim
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From page 4... ...
Two summer research periods were followed by a postdoctoral fellowship from 1933 to 1935 at the Hopkins Marine Station, where Barker began his studies of microbiology under the direction of the distinguished Dutch microbiologist C
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These were production of fatty acids by microbial fermentation, the biochemistry of methanogenesis, and the anaerobic degradation of glutamate. Barker adopted from Kluyver and van Niel the practice of characterizing fermentative pathways by quantitative analysis of the amounts of substrates consumed and products formed.
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6 B I O G R A P H I C A L M E M O I R S When [14C] with its much more convenient long half-life became available in 1944, the use of radiotracer technology for the investigation of metabolic pathways began almost immediately to lead to important and often unexpected findings.
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BIOCHEMISTRY OF METHANE FORMATION Methane fermentations are now known to serve as important anaerobic processes in which the decomposition of a variety of alcohols, amines, and fatty acids is coupled to the reduction of carbon dioxide to methane.
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8 B I O G R A P H I C A L M E M O I R S ane bacteria. During a later postdoctoral appointment in the laboratory of A
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STUDIES OF FATTY ACID METABOLISM WITH CLOSTRIDIUM KLUYVERI During the year he spent in Kluyver's laboratory Barker embarked upon a study designed to test van Niel's theory that the reduction of CO2 to methane might be involved in the fermentation of organic compounds by methane bacteria. To this end Barker prepared anaerobic enrichment cultures containing CaCO3 and ethanol and a generous inoculum of mud from the Delft canal outside Kluyver's laboratory.
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A pure culture of the other microorganism catalyzed the conversion of ethanol and acetic acid to shortchain fatty acids and was given the name Clostridium kluyveri. In subsequent studies one of Barker's students B
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kluyveri undergo autolysis in phosphate buffer, yielding cell-free extracts that contained all of the enzymes involved in the conversion of ethanol and acetate to lower fatty acids. These extracts also could utilize molecular oxygen as an electron acceptor for the oxidation of butyrate and caproate to acetate.
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From page 12... ...
Thus, it became evident that the involvement of postulated intermediates in fatty acid synthesis could be determined by manometric measurements of hydrogen or oxygen consumption when the postulated intermediate was incubated with crude cell-free extracts. Of 15 possible intermediates examined, only 2 -- acetoacetate and vinylacetate -- were metabolized by the extracts, however the roles of these two substances as free intermediates in either butyrate synthesis or oxidation were excluded by a number of criteria.
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In view of the fact that extracts of C kluyveri were found to contain high concentrations of pantothenic acid, Barker proposed that CoA might be implicated in the fatty acid metabolism of this organism.
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From page 14... ...
kluyveri and there was no evidence of any kind to implicate CoA in the oxidation of fatty acids by animal enzyme systems. It is therefore a tribute to Barker's imagination and conceptual analysis that within a few years after his report his hypothesis was shown to be correct in every significant detail, not only in C
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In Barker's laboratory a new Clostridium species that converted lysine to fatty acids and ammonia was isolated. Cell-free extracts were shown
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Remarkably, lysine 2,3-aminomutase resembles the coenzyme B12-dependent enzymes in that it involves enzymebound cobalt and the transient formation of an enzymebound 5-deoxyadenosyl free radical. The latter initiates formation of free-radical forms of lysine (bound in Schiff's base form to pyridoxal phosphate)
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Fatty acid synthesis by enzyme preparations of Clostridium kluyveri.
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Fatty acid synthesis by enzyme preparations of Clostridium kluyveri.
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20 B I O G R A P H I C A L M E M O I R S 1964 With V Rooze, F
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