Equilibrium substrate binding studies of the malic enzyme of pigeon liver. Equivalence of nucleotide sites and anticooperativity associated with the binding of L-malate to the enzyme-manganese(II)-reduced nicotinamide adenine dinucleotide phosphate ternary complex

Biochemistry ◽  
1980 ◽  
Vol 19 (5) ◽  
pp. 951-962 ◽  
Author(s):  
Terry A. Pry ◽  
Robert Y. Hsu
Keyword(s):  
Nicotinamide Adenine Dinucleotide ◽  
Malic Enzyme ◽  
Ternary Complex ◽  
Substrate Binding ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Nicotinamide Adenine ◽  
Binding Studies ◽  
Reduced Nicotinamide Adenine Dinucleotide ◽  
Pigeon Liver

scholarly journals Interactions of nicotinamide-adenine dinucleotide phosphate analogues and fragments with pigeon liver malic enzyme. Synergistic effect between the nicotinamide and adenine moieties

1987 ◽  
Vol 245 (2) ◽  
pp. 407-414 ◽  
Author(s):  
H J Lee ◽  
G G Chang
Keyword(s):  
Synergistic Effect ◽  
Nicotinamide Adenine Dinucleotide ◽  
Malic Enzyme ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Nucleotide Binding ◽  
Phosphate Group ◽  
Nicotinamide Adenine ◽  
Oxidative Decarboxylation ◽  
Wide Range ◽  
Pigeon Liver

The structural requirements of the NADP+ molecule as a coenzyme in the oxidative decarboxylation reaction catalysed by pigeon liver malic enzyme were studied by kinetic and fluorimetric analyses with various NADP+ analogues and fragments. The substrate L-malate had little effect on the nucleotide binding. Etheno-NADP+, 3-acetylpyridine-adenine dinucleotide phosphate, and nicotinamide-hypoxanthine dinucleotide phosphate act as alternative coenzymes for the enzyme. Their kinetic parameters were similar to that of NADP+. Thionicotinamide-adenine dinucleotide phosphate, 3-aminopyridine-adenine dinucleotide phosphate, 5′-adenylyl imidodiphosphate, nicotinamide-adenine dinucleotide 3′-phosphate and NAD+ act as inhibitors for the enzyme. The first two were competitive with respect to NADP+ and non-competitive with respect to L-malate; the other inhibitors were non-competitive with NADP+. All NADP+ fragments were inhibitory to the enzyme, with a wide range of affinity, depending on the presence or absence of a 2′-phosphate group. Compounds with this group bind to the enzyme 2-3 orders of magnitude more tightly than those without this group. Only compounds with this group were competitive inhibitors with respect to NADP+. We conclude that the 2′-phosphate group is crucial for the nucleotide binding of this enzyme, whereas the carboxyamide carbonyl group of the nicotinamide moiety is important for the coenzyme activity. There is a strong synergistic effect between the binding of the nicotinamide and adenosine moieties of the nucleotide molecule.

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