Haeggström J Z, Wetterholm A, Vallee B L, Samuelsson B
Department of Physiological Chemistry, Karolinska Institutet, Stockholm, Sweden.
Biochem Biophys Res Commun. 1990 Nov 30;173(1):431-7. doi: 10.1016/s0006-291x(05)81076-9.
Purified leukotriene A4 hydrolase from human leukocytes is shown to exhibit peptidase activity towards the synthetic substrates alanine-4-nitroanilide and leucine-4-nitroanilide. The enzymatic activity is abolished after heat treatment (70 degrees C, 30 min). At 37 degrees C these substrates are hydrolyzed at a rate of 380 and 130 nmol/mg/min, respectively, and there is no enzyme inhibition during catalysis. Apo-leukotriene A4 hydrolase, obtained by removal of the intrinsic zinc atom, exhibits only a low peptidase activity which can be restored by the addition of stoichiometric amounts of zinc. Reconstitution of the apoenzyme with cobalt results in a peptidase activity which exceeds that of enzyme reactivated with zinc. Preincubation of the native enzyme with leukotriene A4 reduces the peptidase activity. Semipurified preparations of bovine intestinal aminopeptidase and porcine kidney aminopeptidase do not hydrolyze leukotriene A4 into leukotriene B4.
从人白细胞中纯化得到的白三烯A4水解酶对合成底物丙氨酸-4-硝基苯胺和亮氨酸-4-硝基苯胺表现出肽酶活性。热处理（70℃，30分钟）后酶活性丧失。在37℃时，这些底物的水解速率分别为380和130 nmol/mg/分钟，催化过程中没有酶抑制现象。通过去除内在锌原子获得的脱辅基白三烯A4水解酶仅表现出低肽酶活性，添加化学计量的锌可恢复该活性。用钴重组脱辅基酶产生的肽酶活性超过用锌重新激活的酶。天然酶与白三烯A4预孵育会降低肽酶活性。牛小肠氨肽酶和猪肾氨肽酶的半纯化物不能将白三烯A4水解为白三烯B4。
