Lo H H, Yen Y S, Hsieh S E, Chung J G
Department of Medical Technology, Chungtai Junior College, Taichung, Taiwan, Republic of China.
J Appl Toxicol. 1997 Nov-Dec;17(6):385-90. doi: 10.1002/(sici)1099-1263(199711/12)17:6<385::aid-jat455>3.0.co;2-a.
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.
甘草酸是一种被提议用于化学预防的药物，它被用于抑制肺炎克雷伯菌胞质溶胶和完整细菌中的芳胺N - 乙酰转移酶（NAT）活性。通过使用高效液相色谱法测定2 - 乙酰氨基芴和剩余2 - 氨基芴的量来测量NAT活性。甘草酸以剂量依赖性方式抑制肺炎克雷伯菌中的NAT活性。对于2 - 氨基芴的乙酰化反应，在没有甘草酸的情况下，胞质溶胶NAT活性为0.675±0.028 nmol min⁻¹ mg⁻¹蛋白质，在含有8 mM甘草酸的情况下为0.367±0.008 nmol min⁻¹ mg⁻¹蛋白质。从完整细菌中测得的NAT活性，对于2 - 氨基芴的乙酰化反应，在没有甘草酸的情况下为0.308±0.018 nmol min⁻¹ 10⁻¹⁰菌落形成单位，在存在8 mM甘草酸的情况下为0.236±0.005 nmol min⁻¹ 10⁻¹⁰菌落形成单位。甘草酸对NAT活性的抑制作用被证明至少持续4小时。从胞质溶胶NAT计算得出的2 - 氨基芴的表观Km和Vmax值分别为1.08±0.05 mM和9.09±0.11 nmol min⁻¹ mg⁻¹蛋白质。在存在8 mM甘草酸的情况下，2 - 氨基芴的表观Km和Vmax值分别为0.15±0.01 mM和0.95±0.11 nmol min⁻¹ mg⁻¹蛋白质。在完整细菌中，2 - 氨基芴的表观Km和Vmax值分别为1.28±0.48 mM和4.08±1.06 nmol min⁻¹ 10⁻¹⁰菌落形成单位。然而，在存在8 mM甘草酸的情况下，2 - 氨基芴的表观Km和Vmax值分别为0.67±0.09 mM和1.82±0.37 nmol min⁻¹ 10⁻¹⁰菌落形成单位。综合这些结果，甘草酸在胞质溶胶和完整细菌中均抑制肺炎克雷伯菌中的NAT活性。本研究提供了首个证据证明甘草酸可抑制细菌NAT活性。
