Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P39060 (endostatin)
 2,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Glutamine synthetase was purified from the cyanobacterium Anabaena sp. strain CA, a newly isolated marine organism. This organism grows rapidly under nitrogen-fixing conditions and therefore is ideally suited for studies concerning cyanobacterial nitrogen metabolism. Studies were conducted to optimize the production of glutamine synthetase by Anabaena CA. The highest specific activities were obtained from cells grown in the presence of atmospheric N(2) or KNO(3) (13 mM); when NH(4)Cl was used as the nitrogen source, the specific activity was reduced by approximately 40%. Furthermore, through the use of a whole-cell gamma-glutamylhydroxamate transferase assay, it was found that the maximum number of enzyme units is obtained in the late logarithmic stage of growth. Glutamine synthetase purification requires only three steps and results in a preparation that is electrophoretically homogeneous. The transferase specific activity (units per milligram of protein) of the purified enzyme is 78, whereas the biosynthetic specific activity is 2.2. The molecular weight of the native protein was found to be approximately 590,000, and the subunit molecular weight was determined to be about 50,000. Thus, this cyanobacterial enzyme closely resembles the enzyme obtained from other procaryotic sources, at least with regard to size. The purification of glutamine synthetase from Anabaena CA should stimulate a more detailed study of this enzyme and its role in cyanobacterial nitrogen metabolism.
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PMID:Nitrogen and ammonia assimilation in the cyanobacteria: purification of glutamine synthetase from Anabaena sp. strain CA. 2 Nov 67

Glutamine synthetase is the key enzyme in the assimilation by plants of reduced nitrogen provided from either the soil or fixed symbiotically in association with Rhizobium. We have isolated a number of cDNA clones for soybean glutamine synthetase (GS) from a nodule-cDNA library, using RNA from polysomes immunoprecipitated by GS antibodies. Transcripts corresponding to two clones differing in their 3' non-translated sequences were present in both root and nodule tissue; however, the concentration in the nodules was several times higher. The relative concentrations of these sequences in both tissues is about 9:1. Availability of ammonium ions [provided as NH(4)NO(3) or (NH(4))(2)SO(4)] enhanced the expression of both sequences in root tissue within 2 h, reaching a level similar to that in nodules by 8 h, while KNO(3) had no effect during this period. When nitrogen fixation was prevented by replacing nitrogen with argon in the root environment or when the nodules were formed by a Fix mutant of Bradyrhizobium japonicum, the amounts of GS mRNA did not increase over that in roots. These experiments, together with the time course of increase in GS mRNA transcripts, suggest that the genes encoding cytosolic GS are directly induced by the available ammonia.
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PMID:Glutamine synthetase genes are regulated by ammonia provided externally or by symbiotic nitrogen fixation. 1645 62