Phosphodiesterase in the liver fluke, Fasciola hepatica.
Phosphodiesterase in the liver fluke, Fasciola hepatica.
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肝吸虫、肝片形吸虫中的磷酸二酯酶。
DOI：
10.1016/0006-2952(77)90435-x
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发表时间：
1977
影响因子：
5.8
通讯作者：
J. M. Mansour
中科院分区：
文献类型：
--
作者：
T. Mansour;J. M. Mansour
磷酸二酯酶存在于肝片吸虫的匀浆中，并在2000 g离心后分布在上清液和颗粒部分之间。Mg ~（2+）对酶活性有一定的影响，Ca ~（2+）对酶活性无影响。酶动力学符合Michaelis-Menten模型，底物cAMP和cGMP的Km分别为8 μM和300 μM。检测的最有效抑制剂为1-乙基-4-（异亚丙基肼基）-1H-吡唑并-（3，4-B）-吡啶-5-羧酸乙酯，盐酸盐（SQ 20009），其aKi为26 μM。异丁基甲基黄嘌呤（IBMX）的Ki为45 μM; 6，7-二甲基-4-乙基喹唑啉（Quazodine）的Ki为75 μM;罂粟碱的Ki为45 μM。100 μM;茶碱，550 μM;咖啡因或D-麦角酰二乙胺（LSD），800 μM。测定了这些磷酸二酯酶抑制剂对吸虫运动的影响。除咖啡因外，所有磷酸二酯酶抑制剂均能刺激吸虫的节律性运动。测试的抑制剂中没有一种显著增加吸虫头部的内源性cAMP浓度。IBMX可增强5-HT引起的内源性cAMP的升高，而SQ 20009、LSD和罂粟碱则可阻止其升高，后者不能用磷酸二酯酶抑制来解释，而可能是干扰了5-HT对腺苷酸环化酶的刺激。
Phosphodiesterase was found in homogenates of the liver fluke,Fasciola hepatica, and was distributed between a supernatant and particulate fraction after centrifugation at 2000g. Mg2+was necessary for enzyme activity; Ca2+in the presence of Mg2+did not affect enzyme activity. Enzyme kinetics followed the Michaelis-Menten model with aKmof 8 μM for cAMP and 300 μM for cGMP as the substrate. The most potent inhibitor tested was 1-ethyl-4-(isopropylidenehydrazino)-1H-pyrazolo- (3,4-b)-pyridine-5-carboxylic acid, ethyl ester, HC1 (SQ 20009) which had aKiof 26 μM. TheKifor isobutyl methyl xanthine (IBMX) was 45 μM; for 6,7 dimethyl-4 ethylquinazoline (Quazodine) 75 μM; papaverine. 100 μM; theophylline, 550 μM; and for caffeine orD-lysergic acid diethylamide (LSD), 800 μM. The effects on fluke motility of these phosphodiesterase inhibitors were tested. All phosphodiesterase inhibitors except caffeine stimulated the rhythmical movement of the flukes. None of the inhibitors tested significantly increased the endogenous cAMP concentrations of fluke heads. IBMX potentiated the rise in endogenous cAMP caused by 5-hydroxytryptamine (5-HT) but SQ 20009, LSD, and papaverine prevented it. The latter results could not be explained on the basis of phosphodies-terase inhibition, but might be attributed to interference with the stimulation of adenylate cyclase by 5-HT.