Glycyrrhizic acid inhibits arylamine N-acetyltransferase activity in Klebsiella pneumoniae in vitro.

Abstract

Glycyrrhizic acid, one of the proposed chemopreventive drugs, was used to inhibit arylamine N-acetyltransferase (NAT) activity in Klebsiella pneumoniae, both in cytosol and intact bacteria. The NAT activity was measured by using high-performance liquid chromatography to assay the amounts of 2-acetyl-aminofluorene and remaining 2-aminofluorene. The NAT activity in K. pneumoniae was inhibited by glycyrrhizic acid in a dose-dependent manner. The cytosol NAT activities were 0.675 +/- 0.028 nmol min(-1) mg(-1) protein for the acetylation of 2-aminofluorene without glycyrrhizic acid and 0.367 +/- 0.008 nmol min(-1) mg(-1) protein with 8 mM glycyrrhizic acid. The NAT activities measured from intact bacteria were 0.308 +/- 0.018 nmol min(-1) 10(-10) colony forming units for the acetylation of 2-aminofluorene without glycyrrhizic acid and 0.236 +/- 0.005 nmol min(-1) 10(-10) colony forming units in the presence of 8 mM glycyrrhizic acid. The inhibition of NAT activity by glycyrrhizic acid was demonstrated to remain for at least 4 h. The apparent Km and Vmax values calculated from cytosol NAT were 1.08 +/- 0.05 mM and 9.09 +/- 0.11 nmol min(-1) mg(-1) protein, respectively, for 2-aminofluorene. In the presence of 8 mM glycyrrhizic acid, the apparent Km and Vmax values were 0.15 +/- 0.01 mM and 0.95 +/- 0.11 nmol min(-1) mg(-1) protein, respectively, for 2-aminofluorene. In intact bacteria, the apparent Km and Vmax values were 1.28 +/- 0.48 mM and 4.08 +/- 1.06 nmol min(-1) 10(-10) colony forming units, respectively, for 2-aminofluorene. However, in the presence of 8 mM glycyrrhizic acid, the apparent Km and Vmax values were 0.67 +/- 0.09 mM and 1.82 +/- 0.37 nmol min(-1) 10(-10) colony forming units, respectively, for 2-aminofluorene. Taking these results together, the NAT activity in K. pneumoniae was inhibited by glycyrrhizic acid both in cytosol and intact bacteria. This study provides the first evidence to demonstrate that glycyrrhizic acid inhibits bacterial NAT activity.