Rojas-Chaves M, Hellmund C, Walter R D
Department of Biochemical Parasitology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany.
Parasitol Res. 1996;82(5):435-8. doi: 10.1007/s004360050141.
N-Acetyltransferase, which is suggested to be responsible for the production of N1-acetylspermidine in Leishmania amazonensis and to be involved in the process of inactivation and degradation of excessive polyamines, was partially purified and characterized. Among the substrates tested, sym-norspermidine, sym-norspermine, and 1,3-diaminopropane had the highest reaction rates, but the naturally occurring polyamines spermine and spermidine were also acetylated at considerable rates, whereas putrescine was a poor substrate. The Michaelis constants (Km values) for spermine and spermidine were 0.66 and 3.3 mM, respectively. The Km value for acetylcoenzyme A (acetyl-CoA) was determined to be 34 microM. CoA inhibited the reaction in a competitive manner; the inhibition constant was 5 microM. The enzyme showed an apparent relative molecular mass of 35,000.
N-乙酰转移酶在亚马逊利什曼原虫中被认为负责N1-乙酰亚精胺的产生，并参与过量多胺的失活和降解过程，该酶已被部分纯化并进行了表征。在所测试的底物中，对称去甲亚精胺、对称去甲精胺和1,3-二氨基丙烷具有最高的反应速率，但天然存在的多胺精胺和亚精胺也能以相当的速率被乙酰化，而腐胺则是一种较差的底物。精胺和亚精胺的米氏常数（Km值）分别为0.66和3.3 mM。乙酰辅酶A（acetyl-CoA）的Km值测定为34 microM。辅酶A以竞争性方式抑制该反应；抑制常数为5 microM。该酶的表观相对分子质量为35,000。
