Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/38105
標題: Dual functional roles of ATP in the human mitochondrial malic enzyme
作者: Hsu, W.C.
洪慧芝
Hung, H.C.
Tong, L.
Chang, G.G.
關鍵字: pigeon liver
ascaris-suum
analytical ultracentrifugation
oxidative
decarboxylases
regulatory properties
structural stability
magnetic-resonance
crystal-structure
active subunits
lamm equation
期刊/報告no:: Biochemistry, Volume 43, Issue 23, Page(s) 7382-7390.
摘要: Human mitochondrial malic enzyme is a regulatory enzyme with ATP as an inhibitor. Structural studies reveal that the enzyme has two ATP-binding sites, one at the NAD(+)-binding site in the active center and the other at the exo site in the tetramer interface. Inhibition of the enzyme activity is due to the competition between ATP and NAD(+) for the nucleotide-binding site at the active center with an inhibition constant of 81 muM. Binding of the ATP molecule at the exo site, on the other hand, is important for the maintenance of the quaternary structural integrity. The enzyme exists in solution at neutral pH and at equilibrium of the dimer and tetramer with a dissociation constant (K-TD) of 0.67 muM. ATP, at a physiological concentration, shifts the equilibrium toward tetramer and decreases the K-TD by many orders of magnitude. Mutation of a single residue Arg542 at the tetrameric interfacial exo site resulted in dimeric mutants. ATP thus has dual functional roles in the mitochondrial malic enzyme.
URI: http://hdl.handle.net/11455/38105
ISSN: 0006-2960
文章連結: http://dx.doi.org/10.1021/bi049600r
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