Evidence for arylamine N-acetyltransferase in the nematode Anisakis simplex

N-Acetyltransferase activities with p-aminobenzoic acid and 2-aminofluorene were determined in Anisakis simplex, a nematode found in the intestine of the salt water fish Trichiurus lepturus. The N-acetyltransferase activity was determined using an acetyl CoA recycling assay and high pressure liquid chromatography. The N-acetyltransferase activity from a number of Anisakis simplex whole tissue homogenizations was found to be 2.89 ± 0.52 nmol/min per mg for 2-aminofluorene and 2.54 ± 0.45 nmol/min per mg for p-aminobenzoic acid. The Km and Vmax values obtained were 1.06 ± 0.69 mM and 9.34 ± 1.94 nmol/min per mg for 2-aminofluorene, and 2.25 ± 0.10 mM and 14.44 ± 0.7 nmol/min per mg for p-aminobenzoic acid. The optimal pH value for the enzyme activity was pH 8.0 for both substrates tested. The optimal temperature for enzyme activity was 37 °C for both substrates. The N-acetyltransferase activity was inhibited by iodoacetamide: at 0.25 mM iodoacetamide, activity was reduced 50% and 1.0 mM iodoacetamide inhibits activity more than 90%. Among a series of divalent cations and salts, Cu2+ and Zn2+ were demonstrated to be the most potent inhibitors. This is the first demonstration of acetyl CoA/arylamine N-acetyltransferase activity in a nematode and extends the number of phyla in which this activity has been found.