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 aci d and 2-aminofluorene were determined in Helicobacter pylori, a gram-n egative rod bacteria collected from peptic ulcer patients. The NAT act ivity was determined using a acetyl CoA recycling assay and HPLC. Cyto sols or suspensions of H. py[ori with and without selected concentrati ons of emodin co-treatment showed different percentages of 2-aminofluo rene and p-aminobenzoic acid acetylation. The data indicate that there were decreased NAT activity associated with increased emodin in H. py lori cytosols. As 400 mu M of emodin can obviously inhibit NAT activit y both in vitro and in vivo (inhibition rate 90% and 93% for 2-aminofl uorene and p-aminobenzoic acid in vitro, and 90% and 92%, respectively , for both substrate in vivo). For in vitro examination, the apparent values of K-m and V-max were 3.12+/-0.38 mM and 15.20+/-3.16 nmol/min/ mg protein for 2-aminofluorene, and 0.56+/-0.12 mM and 0.74+/-0.09 nmo l/min/mg protein for p-aminobenzoic acid. However, when emodin was add ed to the reaction mixtures, the values of apparent K-m and V-max were 2.40+/-0.32 mM and 10.62+/-0.04 nmol/min/mg protein for 2-aminofluore ne, and 0.23+/-0.02 mM and 0.62+/-0.08 nmol/min/mg protein for p-amino benzoic acid. For in vivo examination, the apparent K-m and V-max were 0.82+/-0.18 mM and 0.92+/-0.21 nmol/min/10x10(10) colony forming unit s (CFU) for 2-aminofluorene, and 0.78+/-0.14 mM and 0.52+/-0.06 nmol/m in/10x10(10) (CFU) for p-aminobenzoic acid. However, when emodin was a dded to the reaction mixtures, the values of apparent K-m and V-max we re 0.50+/-0.08 mM and 0.62+/-0.22 nmol/min/10x10(10) (CFU) for 2-amino fluorene, and 0.52+/-0.21 mM and 0.26+/-0.04 nmol/min/10x10(10) (CFU) for p-aminobenzoic acid. This report is the first finding of emodin in hibition of arylamine N-acetyltransferase activity in a strain of H. p ylori. (C) 1997 Elsevier Science Ltd. All rights reserved.