title: Regulation of coenzyme utilization by mitochondrial NAD(P)-dependent malic enzyme.
abstract: 1. Skeletal muscle mitochondrial NAD(P)-dependent malic enzyme [EC 1.1.1. 39, L-malate:NAD+ oxidoreductase (decarboxylating)] from herring could use both coenzymes, NAD and NADP, in a similar manner. 2. The coenzyme preference of mitochondrial NAD(P)-dependent malic enzyme was probed using dual wavelength spectroscopy and pairing the natural coenzymes, NAD or NADP with their respective thionicotinamide analogues, s-NADP or s-NAD, that have absorbance maxima in reduced forms at 400 nm. 3. s-NAD and s-NADP were found to be good alternate substrates for NAD(P)-dependent malic enzyme, the apparent Km values for the thioderivatives were similar to those of the corresponding natural coenzymes. 4. ATP produced greater inhibition of the NAD or s-NAD linked reactions than of the NADP or s-NADP-linked reactions of skeletal muscle mitochondrial NAD(P)-dependent malic enzyme. 5. At 5 mM malate concentration and in the presence of 2 mM ATP the NADP-linked reaction is favoured and the activity ratios, V(s-NADP)/V(NAD) or V(NADP)/V(s-NAD), are 6 and 26, respectively.
authors.affiliation: Gdańsk University Biological Station, Poland.
authors.forename: E F
authors.initials: EF
authors.lastname: Skorkowski
authors.forename: K B
authors.initials: KB
authors.lastname: Storey
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D005399:Fishes / Q000378:metabolism*; D007700:Kinetics; D008291:Malate Dehydrogenase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008931:Mitochondria, Muscle / Q000201:enzymology*; D009243:NAD / Q000494:pharmacology* / Q000031:analogs & derivatives; D009249:NADP / Q000494:pharmacology* / Q000031:analogs & derivatives; D013053:Spectrophotometry
chemical_list: D009243:NAD; C015541:thionicotinamide adenine dinucleotide phosphate; C003451:thionicotinamide adenine dinucleotide; D009249:NADP; D000255:Adenosine Triphosphate; D008291:Malate Dehydrogenase