Partial purification and characterization of two enzymes from guinea-pig liver microsomes that hydrolyze carcinogenic amides 2-acetylaminofluorene and N-hydroxy-2-acetylaminofluorene

Abstract

Two enzymes capable of deacylating carcinogenic compounds N-hydroxy-2-acetylaminofluorene( N-hydroxy-AAF) and 2-acetyIaminofluorene (AAF) were liberated with sonication from guinea pig liver microsomes. The enzymes were separated by using fractionation with ammonium sulfate, chromatography on Sephadex and hydroxylapatite or DEAE-cellulose. The Enzyme I (mol. wt. 200,000) hydrolyzed N-hydroxy-AAF 265 times faster than AAF, while Enzyme II (mol. wt. 41,000) hydrolyzed AAF about 1.4 times faster than N-hydroxy-AAF. Both enzymes hydrolyzed the acylamido derivatives of fluorene and naphthalene faster than those of benzene. Substitution of the acyl hydrogen atoms enhanced markedly the hydrolysis rates. Both enzymes hydrolyzed readily ester substrates, e.g. tyrosine ethyl ester and 1-naphthyl acetate, and were inhibited by the organic phosphorus compounds.