Inhibitory actions of emodin on arylamine N-acetyltransferase activity in strains of Helicobacter pylori from peptic ulcer patients

Arylamine N-acetyltransferase (NAT) activities with p-aminobenzoic acid and 2-aminofluorene were determined in Helicobacter pylori, a gram-negative rod bacteria collected from peptic ulcer patients. The NAT activity was determined using a acetyl CoA recycling assay and HPLC. Cytosols or suspensions of H. pylori with and without selected concentrations of emodin co-treatment showed different peventages of 2-aminofluorene and p-aminobenzoic acid acetylation. The data indicate that there were decreased NAT activity associated with increased emodin in H. pylori cytosols. As 400 μM of emodin can obviously inhibit NAT activity both in vitro and in vivo (inhibition rate 90% and 93% for 2-aminofluorene and p-aminobenzoic acid in vitro, and 90% and 92%, respectively, for both substrate in vivo). For in vitro examination, the apparent values of Km and Vmax were 3.12 ± 0.38 mm and 15.20 ± 3.16 nmol/min/mg protein for 2-aminofluorene, and 0.56 ± 0.12 m and 0.74 ± 0.09 nmol/min/mg protein for p-aminobenzoic acid. However, when emodin was added to the reaction mixtures, the values of apparent Km and Vmax were 2.40 ± 0.32 mm and 10.62 ± 0.04 nmol/min/mg protein for 2-aminofluorene, and 0.23 ± 0.02 mm and 0.62 ± 0.08 nmol/min/mg protein for p-aminobenzoic acid. For in vivo examination, the apparent Km and Vmax were 0.82 ± 0.18 mm and 0.92 ± 0.21 nmol/min/10 × 1010 colony forming units (CFU) for 2-aminofluorene, and 0.78 ± 0.14 mm and 0.52 ± 0.06 nmol/min/ 10 × 1010 (CFU) for p-aminobenzoic acid. However, when emodin was added to the reaction mixtures, the values of apparent Km and Vmax were 0.50 ± 0.08 mm and 0.62 ± 0.22 nmol/min/ 10 × 1010 (CFU) for 2-aminofluorene, and 0.52 ± 0.21 mm and 0.26 ± 0.04 nmol/min/ 10 × 1010 (CFU) for p-aminobenzoic acid. This report is the first finding of emodin inhibition of arylamine N-acetyltransferase activity in a strain of H. pylori.