Light mediated regulation of nitrate assimilation inSynechococcus leopoliensis

✍ Scribed by Rudolf Tischner; Ahlert Schmidt

• Book ID: 104764793
• Publisher: Springer
• Year: 1984
• Tongue: English
• Weight: 426 KB
• Volume: 137
• Category: Article
• ISSN: 0302-8933
• DOI: 10.1007/bf00414457

✦ Synopsis

Synechococcus leopoliensis was cultivated in a light/dark regime of 12:12 h. After onset of the illumination (2 h), the specific activity of nitrite reductase, glutamine synthetase and isocitric dehydrogenase increased; that of glucose-6-phosphate dehydrogenase decreased and that of nitrate reductase and NAD-(NADP) glutamate dehydrogenase remained nearly unchanged.

This stimulation of the enzymes in vivo was also observed in vitro. Also, when extracts from darkened cells were incubated with thioredoxin and dithioerythriol enzyme activities increased in the same amount as obtained in vivo. In addition, glucose-6-phosphate dehydrogenase and isocitric dehydrogenase were stimulated by Mn 2 + and Mg 2+ in the assay mixture. Glutamine synthetase activity was enhanced only by Mg 2+ while Mn 2 + was inhibitory.

The results are discussed with respect to the regulation of nitrogen metabolism by light.