Asaoka K, Takahashi K
Department of Biochemistry, Kyoto University, Aichi, Japan.
Biochem Pharmacol. 1989 Sep 15;38(18):2977-83. doi: 10.1016/0006-2952(89)90005-1.
The distribution in Japanese monkey tissues of glutathione S-transferase activity toward some aromatic nitro compounds was examined by measuring the release of the nitro group as nitrite ion. The activity was especially high in liver, kidney and small intestine when compounds such as 4-nitroquinoline N-oxide, 5-nitrofurfural diacetal and o-dinitrobenzene were used as substrates. The nitrite-releasing activity of the major enzyme purified from rhesus monkey liver was also tested on fifty-two nitro compounds including nineteen nitrofuran derivatives. Among the thirty-three nitro compounds other than the nitrofuran derivatives tested as substrates, the purified enzyme showed activity only toward o-dinitrobenzene, 4-nitroquinoline N-oxide, 3,4-dinitrobenzoic acid, p-dinitrobenzene, 2,5-dinitrobenzoic acid, 2,5-dinitrophenol, tetra-chloronitrobenzene and 2,4-dinitrobenzoic acid. The crude supernatant fraction of rhesus monkey liver showed activity in substrate specificity roughly similar to that of the purified enzyme. On the other hand, among at least ten carcinogenic 2-substituted 5-nitrofran derivatives tested, 4,6-diamino-2-(5-nitro-2-furyl)-s-triazine, 5-nitro-2-furaldehyde semicarbazone, N-[[3-(5-nitro-2-furyl)-1,2,4-oxadiazol-5-yl]methyl] acetamide, and N-[5-(5-nitro-2-furyl)-1-3,4-thiadiazol-2-yl)acetamide were shown to be enzymatically conjugated with reduced glutathione. Among the other nine 2-substituted 5-nitrofuran derivatives tested, six compounds could be the substrates of the enzyme, and 5-nitrofurfural and 5-nitrofurfural diacetal were especially good substrates. There was, however, little apparent correlation between their carcinogenicity and susceptibility to glutathione S-transferase. The bulky substituents at position 2 appeared to decrease the susceptibility of these nitrofuran derivatives to the enzyme. Both Vmax and Km values of the purified enzyme varied greatly among the substrates, and the optimum pH fell between 7.5 and 9.0 in most cases.
通过测量作为亚硝酸根离子的硝基释放量，研究了日本猕猴组织中谷胱甘肽S -转移酶对某些芳香族硝基化合物的活性分布。当使用4 -硝基喹啉N -氧化物、5 -硝基糠醛二乙酸酯和邻二硝基苯等化合物作为底物时，该活性在肝脏、肾脏和小肠中特别高。还对从恒河猴肝脏中纯化的主要酶对包括19种硝基呋喃衍生物在内的52种硝基化合物的亚硝酸释放活性进行了测试。在作为底物测试的除硝基呋喃衍生物之外的33种硝基化合物中，纯化的酶仅对邻二硝基苯、4 -硝基喹啉N -氧化物、3,4 -二硝基苯甲酸、对二硝基苯、2,5 -二硝基苯甲酸、2,5 -二硝基苯酚、四氯硝基苯和2,4 -二硝基苯甲酸有活性。恒河猴肝脏的粗上清液部分在底物特异性方面表现出与纯化酶大致相似的活性。另一方面，在至少测试的10种致癌性2 -取代5 -硝基呋喃衍生物中，4,6 -二氨基 - 2 - (5 -硝基 - 2 -呋喃基)- s -三嗪、5 -硝基 - 2 -糠醛半卡巴腙、N - [[3 - (5 -硝基 - 2 -呋喃基)- 1,2,4 -恶二唑 - 5 -基]甲基]乙酰胺和N - [5 - (5 -硝基 - 2 -呋喃基)- 1,3,4 -噻二唑 - 2 -基]乙酰胺被证明可与还原型谷胱甘肽进行酶促共轭。在测试的其他9种2 -取代5 -硝基呋喃衍生物中，6种化合物可能是该酶的底物，5 -硝基糠醛和5 -硝基糠醛二乙酸酯是特别好的底物。然而，它们的致癌性与对谷胱甘肽S -转移酶的敏感性之间几乎没有明显的相关性。2位上的大取代基似乎降低了这些硝基呋喃衍生物对该酶的敏感性。纯化酶的Vmax和Km值在不同底物之间差异很大，并且在大多数情况下最适pH值在7.5至9.0之间。
