Identification of the chloramphenicol-hydrolyzing enzyme of guinea pig liver as one of the nonspecific carboxylesterases.
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.
D000818:Animals; D002265:Carboxylic Ester Hydrolases / Q000032:analysis / Q000302:isolation & purification*; D002701:Chloramphenicol / Q000378:metabolism*; D005260:Female; D006168:Guinea Pigs; D006868:Hydrolysis; D008099:Liver / Q000201:enzymology*; D008297:Male; D008970:Molecular Weight; D051381:Rats; D013552:Swine
D002701:Chloramphenicol; D002265:Carboxylic Ester Hydrolases