A novel type of N-acetyltransferase, clearly different from the nuclear and cytosolic polyamine N-acetyltransferases of mammals, was recently found in the intestinal nematode Ascaris suum. The occurrence of this putrescine N-acetylating enzyme has also been noted in the filarial parasite Onchocerca volvulus. The enzyme was partially purified from adults of O. volvulus and A. suum by chromatography on DEAE-cellulose and cadaverine-Sepharose. Substrate specificities of the filarial enzyme resemble those of the N-acetyltransferase from A. suum, with respect to its preference for putrescine and other diamines above polyamines and histones. Additionally, both nematode enzymes acetylated histamine, whereas dopamine and serotonin were not accepted as substrates. The activities of the N-acetyltransferase from O. volvulus and A. suum were potently inhibited by the drug berenil; the type of inhibition was competitive with respect to putrescine. The inhibition constants for berenil were determined as 4.2 and 1.2 microM for the enzymes of O. volvulus and A. suum, the Km values for putrescine were found to be 330 microM and 250 microM, respectively. Putrescine N-acetyltransferase is discussed as a regulatory step in the degradation of excessive polyamines via polyamine oxidase to putrescine. At this branching point, putrescine is retained in the cell for de novo synthesis of spermidine and spermine, catabolized via diamine oxidase or acetylated to a suitable transport product for excretion.

译文

:最近在肠道线虫A虫中发现了一种新型的N-乙酰基转移酶,其明显不同于哺乳动物的核和胞质多胺N-乙酰基转移酶。还已经在丝状寄生虫Onchocerca volvulus中发现了这种腐胺N-乙酰化酶的存在。通过在DEAE-纤维素和尸胺-Sepharose上进行色谱分离,从肠和成虫的成虫中部分纯化该酶。就其对腐胺和其他多胺(高于多胺和组蛋白)的偏好而言,丝状酶的底物特异性类似于来自A. suum的N-乙酰基转移酶。另外,两种线虫酶均使组胺乙酰化,而多巴胺和5-羟色胺不被接受为底物。苯丙胺类药物有效地抑制了来自贪食弧菌和su。suum的N-乙酰基转移酶的活性。抑制类型相对于腐胺具有竞争性。测定苯乙胺醇对肠球菌和猪链球菌的酶的抑制常数为4.2和1.2μM,发现腐胺的Km值分别为330μM和250μM。腐胺N-乙酰基转移酶被讨论为通过聚胺氧化酶将过量的聚胺降解为腐胺的调节步骤。在该分支点,腐胺保留在细胞中,用于从头合成亚精胺和亚精胺,通过二胺氧化酶分解代谢或乙酰化为合适的转运产物以排泄。

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