Evidence for arylamine N-acetyltransferase activity in the bacterium Helicobacter pylori

Abstract

N-Acetyltransferase activities with p-aminobenzoic acid and 2-aminofluorene were determined in Helicobacter pylori from gastroduodenal disease patients. The N-acetyltransferase activity was determined using an acetyl CoA recycling assay and high pressure liquid chromatography. The N-acetyltransferase activities from a number of Helicobacter pylori samples were found to be 0.91 ± 0.12 nmole/min/mg protein for the acetylation of 2-aminofluorene and 0.75 ± 0.22 nmole/min/mg protein for the acetylation of p-aminobenzoic acid. The apparent K m and V max values obtained were 1.10 ± 0.08 mM and 2.34 ± 0.14 nmol/min/mg protein for 2-aminofluorene, and 0.92 ± 0.09 mM and 2.08 ± 0.16 nmol/min/mg protein for p-aminobenzoic acid. The optimal pH value for the enzyme activity was 6.0 for both substrates tested. The optimal temperature for enzyme activity was 37 °C for both substrates. The N-acetyltransferase activity was inhibited by iodacetamide: at 0.25 mM iodacetamide, activity was reduced 50% and 1.0 mM iodacetamide inhibited activity more than 90%. Among a series of divalent cations and salts, Cu 2+ and Zn 2+ were demonstrated to be the most potent inhibitors. Among the protease inhibitors, only ethylenediaminetetraacetic acid significantly protected N-acetyltransferase. Iodoacetic acid, in contrast to the other agents, markedly inhibited N-acetyltransferase. This is the first demonstration of acetyl CoA:arylamine N-acetyltransferase activity in Helicobacter pylori.