Formation of glutamine from (/sup 13/N)ammonia, (/sup 13/N)dinitrogen, and (/sup 14/C)glutamate by heterocysts isolated from Anabaena cylindrica
A method is described for the isolation of metabolically active heterocysts from Anabaena cylindrica. These isolated heterocysts accounted for up to 34% of the acetylene-reducing activity of whole filaments and had a specific activity of up to 1,560 nmol of C/sub 2/H/sub 4/ formed per mg of heterocyst chlorophyll per min. Activity of glutamine synthetase was coupled to activity of nitrogenase in isolated heterocysts as shown by acetylene-inhibitable formation of (/sup 13/N)NH/sub 3/ and of amide-labeled (/sup 13/N)glutamine from (/sup 13/N)N/sub 2/. A method is also described for the production of 6-mCi amounts of (/sup 13/N)NH/sub 3/. Isolated heterocysts formed (/sup 13/N)glutamine from (/sup 13/N)NH/sub 3/ and glutamate, and (/sup 14/C)glutamine from NH/sub 3/ and (/sup 14/C)glutamate, in the presence of magnesium adenosine 5'-triphosphate. Methionine sulfoximine strongly inhibited these syntheses. Glutamate synthase is, after nitrogenase and glutamine synthetase, the third sequential enzyme involved in the assimilation of N/sub 2/ by intact filaments. However, the kinetics of solubilization of the activity of glutamate synthase during cavitation of suspensions of A. cylindrica indicated that very little, if any, of the activity of that enzyme was located in heterocysts. Concordantly, isolated heterocysts failed to form substantial amounts of radioactive glutamate from either (/sup 13/N)glutamine or ..cap alpha..-(/sup 14/C)ketoglutarate in the presence of other substrates and cofactors of the glutamate synthase reaction. However, they formed (/sup 14/C)glutamate rapidly from ..cap alpha..-(/sup 14/C)ketoglutarate by aminotransferase reactions, with various amino acids as the nitrogen donor. The implications of these findings with regard to the identities of the substances moving between heterocysts and vegetative cells are discussed.
- Research Organization:
- Michigan State Univ., East Lansing
- OSTI ID:
- 7221818
- Journal Information:
- J. Bacteriol.; (United States), Vol. 129:3
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BACTERIA
NITROGEN FIXATION
CARBON 14
GLUTAMINE
NITROGEN 13
SYNTHESIS
TRACER TECHNIQUES
AMIDES
AMINO ACIDS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
CARBON ISOTOPES
CARBOXYLIC ACIDS
ELECTRON CAPTURE RADIOISOTOPES
EVEN-EVEN NUCLEI
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
MICROORGANISMS
MINUTES LIVING RADIOISOTOPES
NITROGEN ISOTOPES
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
RADIOISOTOPES
YEARS LIVING RADIOISOTOPES
550701* - Microbiology- Tracer Techniques