Pathway of ammonium assimilation in a marine diatom determined with the radiotracer sup 13 N. [Thalassiosira pseudonoana (Hustedt)]

Journal Article · Thu Dec 01 00:00:00 EST 1988 · Journal of Phycology; (USA)

DOI:https://doi.org/10.1111/j.1529-8817.1988.tb04267.x· OSTI ID:7266753

Zehr, J P ^[1]; Falkowski, P G ^[2]

---

1. State Univ. of New York, Stony Brook (USA)
2. Brookhaven National Laboratory, Upton, NY (USA)

In unicellular algae, ammonium can be assimilated into glutamate through the action of glutamate dehydrogenase (GDH) or into glutamine through the sequential activities of glutamine synthetase and glutamate 2-oxoglutarate amidotransferase (GS-GOGAT pathway). We have shown that the first radio-labeled product of assimilation of {sup 13}NH{sub 4}{sup +} (t{sub {1/2}} = 10 min) was glutamine in the marine diatom Thalassiosira pseudonana (Hustedt). When GS-GOGAT was inhibited with methionine sulfoximine, the incorporation of radioactivity into both glutamine and glutamate was blocked, implying that the radiolabeled glutamate is formed from glutamine. Glutamine was also the first labeled product when the intracellular concentration of ammonium was elevated by preincubation with unlabeled ammonium. The results indicate that the GS-GOGAT pathway is the primary pathway for the assimilation of nitrogen in T. pseudonana.

• DOE Contract Number: AC02-76CH00016
• OSTI ID: 7266753
• Journal Information: Journal of Phycology; (USA), Vol. 24:4; ISSN 0022-3646
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
AMMONIUM COMPOUNDS
METABOLISM
DIATOMS
BIOLOGICAL PATHWAYS
ENZYME ACTIVITY
GLUTAMINE
LABELLED COMPOUNDS
NITRO-GROUP DEHYDROGENASES
NITROGEN
NITROGEN 13
TRACER TECHNIQUES
ALGAE
AMIDES
AMINO ACIDS
BETA DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
CARBOXYLIC ACIDS
CHROMOPHYCOTA
ELECTRON CAPTURE RADIOISOTOPES
ELEMENTS
ENZYMES
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
MINUTES LIVING RADIOISOTOPES
NITROGEN ISOTOPES
NONMETALS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDOREDUCTASES
PLANTS
RADIOISOTOPES
550501* - Metabolism- Tracer Techniques