Interactions of nicotinamide-adenine dinucleotide phosphate analogues and fragments with pigeon liver malic enzyme. Synergistic effect between the nicotinamide and adenine moieties.
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.
Lee
H J
HJ
Department of Biochemistry, National Defense Medical Center, Taipei, Taiwan, Republic of China.
Chang
G G
GG
D000249:Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D010856:Columbidae; D004357:Drug Synergism; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008291:Malate Dehydrogenase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009249:NADP / Q000031:analogs & derivatives* / Q000378:metabolism*; D012267:Ribosemonophosphates / Q000494:pharmacology; D013050:Spectrometry, Fluorescence; D013379:Substrate Specificity
D012267:Ribosemonophosphates; D000249:Adenosine Monophosphate; C031626:ribose-5-phosphate; D009249:NADP; D008291:Malate Dehydrogenase