Inhibition of NAD(H)/NADP(H)--requiring enzymes by aurintricarboxylic acid.
Aurintricarboxylic acid (ATA), an inhibitor of Ca(2+)-dependent endonuclease activity, is often used to implicate a role for increased intracellular calcium in mechanistic toxicology studies. We report here on the ability of ATA to inhibit the activity of several NAD(H)/NADP(H)-requiring enzymes (purified or cellular homogenates), including lactic dehydrogenase, alcohol dehydrogenase, cytochrome c reductase, ethoxycoumarin o-dealkylase, isocitric dehydrogenase, glutathione reductase and glucose-6-phosphate dehydrogenase. These results were compared with the ability of ATA to inhibit micrococcal nuclease and rat liver Ca(2+)-dependent endonuclease activity in similar incubations. With the exception of alcohol dehydrogenase, ATA was a potent inhibitor of each of the purified enzymes, with IC50s ranging from 0.5 to 82 microM. In cell homogenates, however, ATA was from 10 to 100-fold less potent at inhibiting these enzymes. When exogenous protein was added to purified enzyme incubations, the effect of ATA was similarly diminished. Our results demonstrate that ATA inhibits a wide range of NAD(H)/NADP(H)-requiring enzymes in in vitro incubations using purified enzymes, but that the inhibitory effects are markedly reduced in incubations which more closely resemble a cellular milieu.
Thompson
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DC
Department of Medical Pharmacology & Toxicology, College of Medicine, Texas A & M University Health Science Center, College Station 77843-1114, USA.
Reed
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D000818:Animals; D001312:Aurintricarboxylic Acid / Q000378:metabolism / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology; D005954:Glucosephosphate Dehydrogenase / Q000037:antagonists & inhibitors; D008297:Male; D008836:Micrococcal Nuclease / Q000037:antagonists & inhibitors; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism; D009245:NADH Dehydrogenase / Q000037:antagonists & inhibitors; D009247:NADH, NADPH Oxidoreductases / Q000037:antagonists & inhibitors*; D010088:Oxidoreductases / Q000037:antagonists & inhibitors; D010101:Oxygen Consumption / Q000187:drug effects; D014176:Protein Biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D012710:Serum Albumin, Bovine / Q000494:pharmacology
D004791:Enzyme Inhibitors; D012710:Serum Albumin, Bovine; D001312:Aurintricarboxylic Acid; D010088:Oxidoreductases; D005954:Glucosephosphate Dehydrogenase; D009247:NADH, NADPH Oxidoreductases; D009245:NADH Dehydrogenase; D008836:Micrococcal Nuclease