Hui Chung-Sang, Kuo Hsiu-Maan, Yu Chun-Su, Li Te-Mao
Department of Family Medicine, Jen-Ai Hospital, Tali, Taichung, Taiwan, ROC.
J Microbiol Immunol Infect. 2004 Aug;37(4):208-15.
Arylamine N-acetyltransferase (NAT) enzymes have been found in laboratory animals, humans, microorganisms (fungi, bacteria and parasites), and in plants. But the characteristics of NAT from Klebsiella pneumoniae are not clear. NAT activities with p-aminobenzoic acid (PABA) and 2-aminofluorene (AF) as substrates were examined in the cytosol of K. pneumoniae. NAT activity (N-acetylation of substrates) was determined using an acetyl coenzyme A recycling assay and high performance liquid chromatography for determining the amounts of acetylated or non-acetylated PABA or AF. NAT activities from a number of K. pneumoniae isolates were found to be 0.72 +/- 0.08 nmol/min/mg protein for AF, and 0.49 +/- 0.04 nmol/min/mg protein for PABA. The kinetic parameters of apparent Michaelis constant (Km) and maximum velocity (Vmax) obtained were 2.92 +/- 0.48 mM and 7.89 +/- 0.82 nmol/min/mg protein, respectively, for AF and 2.42 +/- 0.28 mM and 9.87 +/- 0.64 nmol/min/mg protein, respectively, for PABA. The optimal pH value for the NAT activity was 7.0 for AF and PABA. The optimal temperature for NAT activity was 37 degrees C for both substrates. The NAT activity was inhibited by 50% with 0.25 mM iodoacetamide, and by more than 90% at 1.0 mM. Among a series of divalent cations and salts, Cu2+ and Zn2+ were the most potent inhibitors of NAT activity.
在实验动物、人类、微生物（真菌、细菌和寄生虫）以及植物中均已发现芳胺N - 乙酰基转移酶（NAT）。但肺炎克雷伯菌中NAT的特性尚不清楚。在肺炎克雷伯菌的胞质溶胶中检测了以对氨基苯甲酸（PABA）和2 - 氨基芴（AF）为底物的NAT活性。使用乙酰辅酶A循环测定法和高效液相色谱法测定乙酰化或未乙酰化的PABA或AF的量，以确定NAT活性（底物的N - 乙酰化）。发现许多肺炎克雷伯菌分离株对AF的NAT活性为0.72±0.08 nmol/分钟/毫克蛋白质，对PABA的NAT活性为0.49±0.04 nmol/分钟/毫克蛋白质。对于AF，获得的表观米氏常数（Km）和最大速度（Vmax）的动力学参数分别为2.92±0.48 mM和7.89±0.82 nmol/分钟/毫克蛋白质，对于PABA分别为2.42±0.28 mM和9.87±0.64 nmol/分钟/毫克蛋白质。NAT活性的最佳pH值对于AF和PABA均为7.0。两种底物的NAT活性的最佳温度均为37℃。NAT活性被0.25 mM碘乙酰胺抑制50％，在1.0 mM时抑制超过90％。在一系列二价阳离子和盐中，Cu2 +和Zn2 +是NAT活性最有效的抑制剂。
