02141nas a2200169   4500008004100000245010600041210006900147260000800216300001400224490000700238520150200245100002401747700002601771700002601797700002101823856012701844       2017                        eng d00aExploring the role of GS-GOGAT cycle in microcystin synthesis and regulation - a model based analysis0 aExploring the role of GSGOGAT cycle in microcystin synthesis and  cDEC  a2603-26140 v133 aToxic cyanobacteria blooms populate water bodies by consuming external nutrients and releasing cyanotoxins that are detrimental for other aquatic species, producing a significant impact on the plankton ecosystem and food web. To exercise population-level control of toxin production, understanding the biochemical mechanisms that explain cyanotoxin regulation within a bacterial cell is of utmost importance. In this study, we explore the mechanistic events to investigate the dependence of toxin microcystin on external nitrogen, a known regulator of the toxin, and for the first time, propose a kinetic model that analyzes the intracellular conditions required to ensure nitrogen dependence on microcystin. We hypothesize that the GS-GOGAT cycle is manipulated by variable influx of different intracellular metabolites that can either disturb or promote the balance between the enzyme microcystin synthetase and substrate glutamate to produce variable microcystin levels. As opposed to the popular notion that nitrogen starvation increases microcystin synthesis, our analyses suggest that under certain intracellular metabolite regimes, this relationship can either be completely lost or reversed. External nitrogen can only complement the conditions fixed by intracellular glutamate, glutamine and 2-oxoglutarate. This mechanistic understanding can provide an experimentally testable hypothesis for exploring the less-known biology of microcystin synthesis and designing specific interventions.1 aBanerjee, Swarnendu1 aSubramanian, Abhishek1 aChattopadhyay, Joydev1 aSarkar, Ram, Rup  uhttps://library.ncl.res.in/content/exploring-role-gs-gogat-cycle-microcystin-synthesis-and-regulation-model-based-analysis