caa a22 4500 477100473 CHVBK 20180405111539.0 cr unu---uuuuu 170330e19960101xx s 000 0 eng 10.1007/BF00197582 doi (NATIONALLICENCE)springer-10.1007/BF00197582 Regulation of nitrate assimilation in the cyanobacterium Phormidium laminosum [Elektronische Daten] [María Tapia, María Llama, Juan Serra] The intracellular ratio of 2-oxoglutarate to glutamine has been analyzed under nutritional conditions leading to different activity levels of nitrate-assimilating enzymes in Phormidium laminosum (Agardh) Gom. This non-N2-fixing cyanobacterium adapted to the available nitrogen source by modifying its nitrate reductase (NR; EC 1.7.7.2), nitrite reductase (NiR; EC 1.7.7.1) and glutamine synthetase (GS; EC 6.3.1.2) activities. The 2-oxoglutarate/glutamine ratio was similar in cells adapted to grow with nitrate or ammonium. However, metabolic conditions that increased this ratio [i.e., nitrogen starvation or l-methionine-d,l-sulfoximine (MSX) treatment] corresponded to high activity levels of NR, NiR, GS (except in MSX-treated cells) and glutamate synthase (GOGAT; EC 1.4.7.1). By contrast, metabolic conditions that diminished this ratio (i.e., addition of ammonium to nitrate-growing cells or addition of nitrate or ammonium to nitrogen-starved cells) resulted in low activity levels. The variation in the 2-oxoglutarate/glutamine ratio preceded the changes in enzyme activities. These results suggest that changes in the 2-oxoglutarate/glutamine ratio could be the signal that triggers the adaptation of P. laminosum cells to variations in the available nitrogen source, as occurs in enterobacteria. Springer-Verlag, 1996 Carbon-nitrogen interactions nationallicence Glutamine nationallicence Nitrate and ammonium assimilation nationallicence Nitrogen regulation nationallicence 2-Oxoglutarate nationallicence Phormidium nationallicence Chl : chlorophyll nationallicence GOGAT : ferredoxin-dependent glutamate synthase (EC 1.4.7.1) nationallicence GS : glutamine synthetase (EC 6.3.1.2) nationallicence MSX : l-methionine-d,l-sulfoximine nationallicence NiR : nitrite reductase (EC 1.7.7.1) nationallicence NR : nitrate reductase (EC 1.7.7.2) nationallicence TP : total protein nationallicence Tapia María Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias, Universidad del País Vasco, Apartado 644, E-48080, Bilbao, Spain aut Llama María Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias, Universidad del País Vasco, Apartado 644, E-48080, Bilbao, Spain aut Serra Juan Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias, Universidad del País Vasco, Apartado 644, E-48080, Bilbao, Spain aut Planta Springer-Verlag 198/1(1996-01-01), 24-30 0032-0935 198:1<24 1996 198 425 https://doi.org/10.1007/BF00197582 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00197582 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Tapia María Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias, Universidad del País Vasco, Apartado 644, E-48080, Bilbao, Spain aut NATIONALLICENCE 700 1- Llama María Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias, Universidad del País Vasco, Apartado 644, E-48080, Bilbao, Spain aut NATIONALLICENCE 700 1- Serra Juan Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias, Universidad del País Vasco, Apartado 644, E-48080, Bilbao, Spain aut NATIONALLICENCE 773 0- Planta Springer-Verlag 198/1(1996-01-01), 24-30 0032-0935 198:1<24 1996 198 425 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer