title: A mathematical model for the adenylosuccinate synthetase reaction involved in purine biosynthesis.
abstract: BACKGROUND
  Development of the mathematical models that adequately describe biochemical reactions and molecular-genetic mechanisms is one of the most important tasks in modern bioinformatics. Because the enzyme adenylosuccinate synthetase (AdSS) has long been extensively studied, a wealth of kinetic data has been accumulated.
  
  
  RESULTS
  We describe a mathematical model for the reaction catalyzed by AdSS. The model's parameters were fitted to experimental data obtained from published literature. The advantage of our model is that it includes relationships between the reaction rate, the concentrations of three substrates (GTP, IMP and ASP), the effects of five inhibitors (GMP, GDP, AMP, ASUC and SUCC), and the influence of Mg2+ ions.
  
  
  CONCLUSIONS
  Our model describes the reaction catalyzed by AdSS as a fully random process. The model structure implies that each of the inhibitors included in it is only competitive to one of the substrates. The model was tested for adequacy using experimental data published elsewhere. The values obtained for the parameters are as follows: Vmax = 1.35.10-3 mM/min, KmGTP = 0.023 mM, KmIMP = 0.02 mM, KmASP = 0.3 mM, KiGMP = 0.024 mM, KiGDP = 8.10-3 mM, KiAMP = 0.01 mM, KiASUC = 7.5.10-3 mM, KiSUCC = 8 mM, KmMg = 0.08 mM.
authors.affiliation: Institute of Cytology and Genetics SB RAS, Novosibirsk, Russia. nzhenia@bionet.nsc.ru
authors.forename: Evgeniya A
authors.initials: EA
authors.lastname: Oshchepkova-Nedosekina
authors.forename: Vitalii A
authors.initials: VA
authors.lastname: Likhoshvai
mesh_terms: D000265:Adenylosuccinate Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D001224:Aspartic Acid / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology; D006160:Guanosine Triphosphate / Q000378:metabolism; D007291:Inosine Monophosphate / Q000378:metabolism; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008954:Models, Biological; D011687:Purines / Q000096:biosynthesis*; D013379:Substrate Specificity
chemical_list: D004791:Enzyme Inhibitors; D011687:Purines; D007291:Inosine Monophosphate; D001224:Aspartic Acid; D006160:Guanosine Triphosphate; D000265:Adenylosuccinate Synthase; D008274:Magnesium; C030985:purine