title: Purification and comparative properties of isoenzymes of nicotinamide-adenine dinucleotide phosphate-isocitrate dehydrogenase from rat heart and liver.
abstract: 1. Rat liver and heart major isoenzymes of NADP-isocitrate dehydrogenase have each been purified about 100-fold by a combination of ammonium sulphate fractionation and chromatography on ion-exchange cellulose and their properties compared. 2. The properties were similar in respect of pH, inhibition by Hg(2+) and Michaelis constants for isocitrate and NADP. 3. Some of the properties of the isoenzymes were different. 4. The heart isoenzyme was activated about 210% by 0.8m-ammonium sulphate whereas the liver isoenzyme was unaffected. The heart isoenzyme showed greater sensitivity to inactivation by heat (30 degrees C for 30min), whereas the liver isoenzyme was more sensitive to inactivation by p-chloromercuribenzoate and by Cu(2+). 5. The Michaelis constants with 3-acetylpyridine-adenine dinucleotide phosphate showed a twofold difference between liver and heart isoenzyme. 6. The differential sensitivity to heat and its mainly non-cytoplasmic location may be an explanation of the failure of plasma isocitrate dehydrogenase activity to increase after a myocardial infarction.
mesh_terms: D000818:Animals; D002848:Chromatography, DEAE-Cellulose; D002852:Chromatography, Ion Exchange; D003300:Copper / Q000494:pharmacology; D004592:Electrophoresis, Starch Gel; D006863:Hydrogen-Ion Concentration; D007521:Isocitrate Dehydrogenase / Q000037:antagonists & inhibitors / Q000302:isolation & purification; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000302:isolation & purification; D008099:Liver / Q000201:enzymology*; D008297:Male; D008628:Mercury / Q000494:pharmacology; D009206:Myocardium / Q000201:enzymology*; D009249:NADP; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D051381:Rats; D013431:Sulfates / Q000494:pharmacology; D013696:Temperature
chemical_list: D007527:Isoenzymes; D000644:Quaternary Ammonium Compounds; D013431:Sulfates; D009249:NADP; D003300:Copper; D007521:Isocitrate Dehydrogenase; D008628:Mercury