title: Quaternary structure of pigeon liver malic enzyme.
abstract: Pigeon liver malic enzyme (EC 1.1.1.40) has a double dimer quaternary structure. The NADP+ analogs, aminopyridine adenine dinucleotide phosphate and nicotinamide-1,N6-ethenoadenosine dinucleotide phosphate, bind to the enzyme anti-cooperatively. In the presence of non-cooperative competing ligand NADP+, the binding parameter Hill coefficients of these analogues changed very little. Binding of L-malate with enzyme-AADP+ complex first enhanced then reduced the nucleotide fluorescence. Two L-malate binding sites, with Kd values of 23-30 and 270-400 microM, respectively. for the tight and weak binding sites were postulated. A hybrid model between the sequential and pre-existing asymmetrical models was proposed for the pigeon liver malic enzyme.
authors: Department of Biochemistry, National Defense Medical Center, Taipei, Taiwan, Republic of China.
authors: H J
authors: HJ
authors: Lee
authors: G G
authors: GG
authors: Chang
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D010856:Columbidae; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D008291:Malate Dehydrogenase / Q000378:metabolism; D008293:Malates / Q000378:metabolism; D015394:Molecular Structure; D009249:NADP / Q000378:metabolism
chemical_list: D008293:Malates; D009249:NADP; D000244:Adenosine Diphosphate; C030298:malic acid; D008291:Malate Dehydrogenase