Kuhn D, Heymann E
Biochem Pharmacol. 1982 Mar 1;31(5):781-6. doi: 10.1016/0006-2952(82)90463-4.
Guinea pig liver has the highest chloramphenicol-hydrolyzing capacity among the livers of various mammals. The enzyme responsible for the hydrolysis of the amide-bond in chloramphenicol is one of the isoenzymes of the microsomal nonspecific carboxylesterases. This isoenzyme is related to the well-known acetanilide-hydrolyzing carboxylesterases/amidases of pig and rat liver. The guinea pig liver enzyme is purified 24-fold starting with microsomes. The purified enzyme is essentially free from other proteins except other carboxylesterase isoenzymes with similar properties. The chloramphenicol-hydrolyzing esterase has an apparent molecular weight of about 180,000, a subunit weight of 60,000 and a pH optimum at 8.5. It also hydrolyzes methyl butyrate and acetanilide and it is completely inhibited by diethyl-4-nitrophenyl phosphate. Two assay procedures for the enzymatic chloramphenicol hydrolysis are described: a thin-layer chromatographic assay using radioactive chloramphenicol and a colorimetric assay utilizing the reaction of the liberated amine with trinitrobenzenesulfonic acid.
豚鼠肝脏在各种哺乳动物肝脏中具有最高的氯霉素水解能力。负责水解氯霉素中酰胺键的酶是微粒体非特异性羧酸酯酶的同工酶之一。这种同工酶与猪和大鼠肝脏中著名的水解乙酰苯胺的羧酸酯酶/酰胺酶有关。豚鼠肝脏酶从微粒体开始纯化了24倍。纯化后的酶除了具有相似性质的其他羧酸酯酶同工酶外，基本上不含其他蛋白质。氯霉素水解酯酶的表观分子量约为180,000，亚基分子量为60,000，最适pH为8.5。它还能水解丁酸甲酯和乙酰苯胺，并且完全被对硝基苯基磷酸二乙酯抑制。描述了两种酶促氯霉素水解的测定方法：一种使用放射性氯霉素的薄层色谱测定法和一种利用释放的胺与三硝基苯磺酸反应的比色测定法。
