Kinetic studies of asparagine synthetase from rat liver: role of Mg2+ in enzyme catalysis |
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| Authors: | S Hongo T Sato |
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| Institution: | 1. Department of Chemistry, Mar Ivanios College (Autonomous), (Research Centre: University of Kerala), Nalanchira, Thiruvananthapuram, 695015, Kerala, India;2. Department of Glass Processing, FunGlass, Alexander Dubček University of Trenčín, Študentská 2, 911 50, Trenčín, Slovakia;3. Department of Physics, University of Kerala, Karaiavttom, Thiruvananthapuram, 695581, Kerala, India;4. Department of Biochemistry, St. Albert’s College (Autonomous), Ernakulam, 682018, Kerala, India;1. Key Laboratory of Cluster Science of Ministry of Education, Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, School of Chemistry, Beijing Institute of Technology, Beijing 100081, PR China;2. Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3113, United States |
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| Abstract: | The kinetic mechanism of asparagine synthetase from rat liver has been studied. The mechanism of the reaction in the presence of high concentrations of total Mg2+ (50 mM) was suggested to be a uni-uni-bi-ter ping-pong-type without abortive complexes; glutamine binds first followed by glutamate release, and aspartate and ATP bind in order followed by ordered release of PPi, AMP, and asparagine. But, it is indicated that in the presence of 0.5-2.0 mM excess Mg2+ over ATP the binding of substrates after the release of glutamate is in a rapid equilibrium system such as ordered Mg2+ and random aspartate-MgATP. Mg2+ was demonstrated to have two roles in the catalysis; to modify the enzyme and to form a complex of MgATP. |
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