Chiarugi A, Moroni F
Department of Preclinical and Clinical Pharmacology, University of Florence, Italy.
J Neurochem. 1999 Mar;72(3):1125-32. doi: 10.1046/j.1471-4159.1999.0721125.x.
The use of o-methoxybenzoylalanine, a selective kynureninase inhibitor, has been proposed with the aim of reducing brain synthesis of quinolinic acid, an excitotoxic tryptophan metabolite. In liver homogenates, however, this compound caused unexpected accumulation of 3-hydroxyanthranilic acid, the product of kynureninase activity and the precursor of quinolinic acid. To explain this observation, we investigated the interaction(s) of o-methoxybenzoylalanine with 3-hydroxyanthranilic acid dioxygenase, the enzyme responsible for quinolinic acid formation. When the purified enzyme or partially purified cytosol preparations were used, o-methoxybenzoylalanine did not affect 3-hydroxyanthranilic acid dioxygenase activity. However, a significant reduction of this enzymatic activity did occur when o-methoxybenzoylalanine was tested in the presence of mitochondria. It is interesting that addition of purified mitochondria to 3-hydroxyanthranilic acid dioxygenase preparations reduced the enzymatic activity and the synthesis of quinolinic acid. In vivo, administration of o-methoxybenzoylalanine significantly reduced quinolinic acid synthesis and content in both blood and brain of mice. Our results suggest that mitochondrial protein(s) interact(s) with soluble 3-hydroxyanthranilic acid dioxygenase and cause(s) modifications in the enzyme resulting in a decrease in its activity. These modifications also allow the enzyme to interact with o-methoxybenzoylalanine, thus leading to a further reduction in quinolinic acid synthesis.
有人提出使用邻甲氧基苯甲酰丙氨酸，一种选择性犬尿氨酸酶抑制剂，目的是减少喹啉酸在大脑中的合成，喹啉酸是一种具有兴奋性毒性的色氨酸代谢产物。然而，在肝脏匀浆中，这种化合物导致了3-羟基邻氨基苯甲酸意外积累，3-羟基邻氨基苯甲酸是犬尿氨酸酶活性的产物以及喹啉酸的前体。为了解释这一现象，我们研究了邻甲氧基苯甲酰丙氨酸与3-羟基邻氨基苯甲酸双加氧酶（负责喹啉酸形成的酶）之间的相互作用。当使用纯化的酶或部分纯化的胞质溶胶制剂时，邻甲氧基苯甲酰丙氨酸不影响3-羟基邻氨基苯甲酸双加氧酶的活性。然而，当在有线粒体存在的情况下测试邻甲氧基苯甲酰丙氨酸时，这种酶的活性确实出现了显著降低。有趣的是，向3-羟基邻氨基苯甲酸双加氧酶制剂中添加纯化的线粒体降低了酶活性以及喹啉酸的合成。在体内，给予邻甲氧基苯甲酰丙氨酸显著降低了小鼠血液和大脑中喹啉酸的合成及含量。我们的结果表明，线粒体蛋白与可溶性3-羟基邻氨基苯甲酸双加氧酶相互作用，并导致该酶发生修饰，从而使其活性降低。这些修饰还使该酶能够与邻甲氧基苯甲酰丙氨酸相互作用，进而导致喹啉酸合成进一步减少。
