Plaut G W, Aogaichi T, Gabriel J L
Arch Biochem Biophys. 1986 Feb 15;245(1):114-24. doi: 10.1016/0003-9861(86)90195-5.
The RS-isomers of beta-mercapto-alpha-ketoglutarate, beta-methylmercapto-alpha-ketoglutarate and beta-methylmercapto-alpha-hydroxyglutarate have been synthesized. Beta-Mercapto-alpha-ketoglutarate was a potent inhibitor, competitive with isocitrate and noncompetitive with NADP+, of the mitochondrial NADP-specific isozyme from pig heart (Ki = 5 nM; Km (DL-isocitrate)/Ki(RS-beta-mercapto-alpha-ketoglutarate) = 650) and pig liver, the cytosolic isozyme from pig liver (I0.5 = 23 nM), and the NADP-linked enzymes from yeast (Ki = 58 nM) and Escherichia coli (Ki = 58 nM) at pH 7.4 and with Mg2+ as activator. beta-Mercapto-alpha-ketoglutarate was also an effective inhibitor of NADP-isocitrate-dehydrogenase activity in intact liver mitochondria. beta-Mercapto-alpha-ketoglutarate was a much less potent inhibitor for heart NAD-isocitrate dehydrogenase (Ki = 520 nM) than for the NADP-specific enzyme. beta-Methylmercapto-alpha-ketoglutarate (I0.5 = 10 microM) was a much less effective inhibitor than the beta-mercapto derivative for heart NADP-isocitrate dehydrogenase. The beta-sulfur substituted alpha-ketoglutarates were substrates for the oxidation of NADPH by heart NADP-isocitrate dehydrogenase without requiring CO2. beta-Methylmercapto-alpha-hydroxyglutarate, the expected product of reduction of beta-methylmercapto-alpha-ketoglutarate, did not cause reduction of NADP+ but it was an inhibitor competitive with isocitrate for NADP-isocitrate dehydrogenase. The beta-sulfur substituted alpha-ketoglutarate derivatives were alternate substrates for alpha-ketoglutarate dehydrogenase and the cytosolic and mitochondrial isozymes of heart aspartate aminotransferase but had no effect on glutamate dehydrogenase or alanine aminotransferase.
已合成了β-巯基-α-酮戊二酸、β-甲基巯基-α-酮戊二酸和β-甲基巯基-α-羟基戊二酸的RS-异构体。β-巯基-α-酮戊二酸是一种强效抑制剂，在pH 7.4且以Mg2+作为激活剂时，它对猪心线粒体NADP特异性同工酶（Ki = 5 nM；Km(DL-异柠檬酸)/Ki(RS-β-巯基-α-酮戊二酸)= 650）和猪肝线粒体NADP特异性同工酶、猪肝胞质同工酶（I0.5 = 23 nM）以及酵母（Ki = 58 nM）和大肠杆菌（Ki = 58 nM）的NADP连接酶具有竞争性抑制作用，对异柠檬酸为竞争性抑制，对NADP+为非竞争性抑制。β-巯基-α-酮戊二酸也是完整肝线粒体中NADP-异柠檬酸脱氢酶活性的有效抑制剂。β-巯基-α-酮戊二酸对心脏NAD-异柠檬酸脱氢酶（Ki = 520 nM）的抑制作用比对NADP特异性酶的抑制作用弱得多。β-甲基巯基-α-酮戊二酸（I0.5 = 10 μM）对心脏NADP-异柠檬酸脱氢酶的抑制作用比β-巯基衍生物弱得多。β-硫取代的α-酮戊二酸是心脏NADP-异柠檬酸脱氢酶氧化NADPH的底物，无需CO2。β-甲基巯基-α-羟基戊二酸是β-甲基巯基-α-酮戊二酸还原的预期产物，它不会导致NADP+还原，但它是NADP-异柠檬酸脱氢酶的抑制剂，对异柠檬酸具有竞争性抑制作用。β-硫取代的α-酮戊二酸衍生物是α-酮戊二酸脱氢酶以及心脏天冬氨酸氨基转移酶的胞质和线粒体同工酶的替代底物，但对谷氨酸脱氢酶或丙氨酸氨基转移酶没有影响。
