ISSN:
1432-072X
Keywords:
Key words: Pyrococcus furiosus – Hyperthermophile – Archaea – Fermentation –l-alanine – Alanine aminotransferase – Glutamate dehydrogenase – Interspecies hydrogen transfer
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract. The hyperthermophilic archaeon Pyrococcus furiosus was found to form substantial amounts of l-alanine during batch growth on either cellobiose, maltose or pyruvate. Acetate, CO2 and H2 were produced next to alanine. The carbon- and electron balances were complete for all three substrates. Under standard growth conditions (N2/CO2 atmosphere) an alanine/acetate ratio of about 0.3 was found for either substrate. The alanine/acetate ratio was influenced, however, by the hydrogen partial pressure. In the presence of S0 or in coculture with Methanococcus jannaschii this ratio was only 0.07, whereas under a H2/CO2 atmosphere this ratio could amount up to 0.8. Alanine formation was also affected by the NH |lefbop| + |clobop||opnbop| 4 |clobop| concentration, i.e. below 4 mM, NH |lefbop| + |clobop||opnbop| 4 |clobop| becomes limiting to alanine formation. Alanine formation was shown to occur via an alanine aminotransferase, which exhibited a specific activity in cell-free extract of up to 6.0 U/mg (90 °C; direction of pyruvate formation). The alanine aminotransferase probably cooperates with glutamate dehydrogenase (up to 23 U/mg; 90 °C) and ferredoxin: NADP+ oxidoreductase (up to 0.7 U/mg, using methyl viologen; 90 °C) to recycle the electron acceptors involved in catabolism. Thus, the existence of this unusual alanine-forming branch enables P. furiosus to adjust its fermentation, depending on the redox potential of the terminal electron acceptor.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00276479
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