Purification and characterization of a rat liver enzyme catalyzing N-deacetylation of mercapturic acid conjugates.

An enzyme catalyzing N-deacetylation of both S-aryl- and S-aralkylmercapturic acids has been purified about 1000-fold from rat liver cytosol. The enzyme is distinct from N-acetyl-beta-alanine deacylase [EC 3.5.1.21], epsilon-acyllysine deacylase [EC 3.5.1.17], acylase I [EC 3.5.1.14], and acylase II [EC 3.5.1.15] but resembles acylase III with regard to the substrate specificity. The KM value for N-acetyl-S-(p-nitrobenzyl)-L-cysteine was 0.38 mM at optimum pH (8.5) in Tris/HCl buffer. The molecular weight of the purified deacetylase determined by gel-filtration was 145,000 +/- 10,000.