Marhevka V C, Ebner N A, Sehon R D, Hanna P E
J Med Chem. 1985 Jan;28(1):18-24. doi: 10.1021/jm00379a005.
N-Arylhydroxamic acid N,O-acyltransferase (AHAT) catalyzes the transfer of the N-acetyl group from N-arylhydroxamic acids to arylamines. In the absence of an arylamine acceptor, AHAT catalyzes the conversion of N-arylhydroxamic acids to reactive electrophilic intermediates that become irreversibly bound to cellular nucleophiles, including those present on AHAT itself. As part of an investigation of the AHAT-catalyzed bioactivation process, a series of 7-substituted analogues of N-hydroxy-2-acetamidofluorene (1) was synthesized and evaluated in vitro as substrates and inactivators of a partially purified hamster hepatic AHAT preparation. All of the compounds functioned as acetyl donors in the AHAT-catalyzed transacetylation of 4-aminoazobenzene (AAB) and all of them were inactivators of AHAT. The inactivation process exhibited apparent first-order kinetics, and the 7-methoxy compound exhibited the largest inactivation rate constant. Quantitative structure-activity analysis provided support for the concept that positively charged species are involved in the inactivation of AHAT by this series of compounds. Results of experiments in which nucleophilic trapping agents such as glutathione, cysteine, methionine, guanosine phosphate, and tRNA were included in incubation mixtures with AHAT and the N-arylhydroxamic acids indicated that electrophiles which diffuse away from the enzyme active site participate in the inactivation process.
N-芳基异羟肟酸N,O-酰基转移酶（AHAT）催化N-芳基异羟肟酸的N-乙酰基转移至芳胺。在没有芳胺受体的情况下，AHAT催化N-芳基异羟肟酸转化为反应性亲电中间体，这些中间体与细胞亲核试剂不可逆结合，包括AHAT自身上存在的亲核试剂。作为对AHAT催化的生物活化过程研究的一部分，合成了一系列N-羟基-2-乙酰氨基芴（1）的7-取代类似物，并在体外作为部分纯化的仓鼠肝AHAT制剂的底物和失活剂进行评估。所有化合物在AHAT催化的4-氨基偶氮苯（AAB）转乙酰化反应中均作为乙酰基供体，并且它们都是AHAT的失活剂。失活过程表现出明显的一级动力学，7-甲氧基化合物表现出最大的失活速率常数。定量构效分析为该系列化合物使AHAT失活涉及带正电物种这一概念提供了支持。在与AHAT和N-芳基异羟肟酸的孵育混合物中加入亲核捕获剂如谷胱甘肽、半胱氨酸、甲硫氨酸、磷酸鸟苷和tRNA的实验结果表明，从酶活性位点扩散出去的亲电试剂参与了失活过程。
