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Title Anaerobic carbon metabolism by the tricarboxylic acid cycle
Creator/Author Vanlerberghe, G.C. ; Horsey, A.K. ; Weger, H.G. ; Turpin, D.H. (Queen`s Univ., Kingston, Ontario (Canada))
Publication Date1989 Dec 01
OSTI IdentifierOSTI ID: 5962276
Other Number(s)ISSN0032-0889; CODEN: PLPHA
Resource TypeJournal Article
Resource RelationPlant Physiology ; Vol/Issue: 91:4
Subject550201 -- Biochemistry-- Tracer Techniques; ANOXIA-- BIOLOGICAL EFFECTS; ANAEROBIC CONDITIONS;CARBON 14 COMPOUNDS;CELL CULTURES;OXIDOREDUCTASES;TRACER TECHNIQUES
Related SubjectENZYMES;ISOTOPE APPLICATIONS;LABELLED COMPOUNDS
Description/Abstract Nitrogen-limited cells of Selenastrum minutum (Naeg.) Collins are able to assimilate NH{sub 4}{sup +} in the dark under anaerobic conditions.^Addition of NH{sub 4}{sup +} to anaerobic cells results in a threefold increase in tricarboxylic acid cycle (TCAC) CO{sub 2} efflux and an eightfold increase in the rate of anaplerotic carbon fixation via phosphoenspyruvate carboxylase.^Both of these observations are consistent with increased TCAC carbon flow to supply intermediates for amino acid biosynthesis.^Addition of H{sup 14}CO{sub 3}{sup {minus}} to anaerobic cells assimilating NH{sub 4}{sup +} results in the incorporation of radiolabel into the {alpha}-carboxyl carbon of glutamic acid.^Incorporation of radiolabel into glutamic acid is not simply a short-term phenomenon following NH{sub 4}{sup +} addition as the specific activity of glutamic acid increases over time.^This indicates that this alga is able to maintain partial oxidative TCAC carbon flow while under anoxia to supply {alpha}ketoglutarate for glutamate production.^During dark aerobic NH{sub 4}{sup +} assimilation, no radiolabel appears in fumarate or succinate and only a small amount occurs in malate.^During anaerobic NH{sub 4}{sup +} assimilation, these metabolites contain a large proportion of the total radiolabel and radiolabel accumulates in succinate over time.^Also, the ratio of dark carbon fixation to NH{sub 4}{sup +} assimilation is much higher under anaerobic than aerobic conditions.^These observations suggest the operation of a partial reductive TCAC from oxaloacetic acid to malate, fumarate, and succinate.^Such a pathway might contribute to redox balance in an anaerobic cell maintaining partial oxidative TCAC activity.
Country of PublicationUnited States
LanguageEnglish
FormatPages: 1551-1557
System Entry Date2001 May 13

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