Glatt H R, Wölfel T, Oesch F
Biochem Biophys Res Commun. 1983 Jan 27;110(2):525-9. doi: 10.1016/0006-291x(83)91181-6.
Epoxide hydrolase (epoxide hydratase, epoxide hydrase, E.C. 3.3.2.3) activity so far has only been measured in subcellular preparations. We show here that, with the highly lipophilic substrate (3H)-benzo(a)pyrene 4,5-oxide, the activity can be determined in intact cells. Whole human lymphocytes hydrolyze it at a similar rate to that in lymphocyte homogenate. We have previously reported that cultivation of lymphocytes in a medium containing 5,6-benzoflavone leads to an increase in epoxide hydrolase activity. We now demonstrate that this stimulation is due to enzyme activation and that enzyme induction does not contribute to this increase to any measurable extent. Moreover, both 5,6-benzoflavone and 7,8-benzoflavone activate epoxide hydrolase. This activation occurs not only in cell homogenate, but also - with a similar concentration-response relationship - in whole lymphocytes. Hence measurement of epoxide hydrolase activity in subcellular preparations reflects the activity in these intact cells. Furthermore, insofar as a concentration of 1 microM of the benzoflavones is sufficient to cause a measurable (10 to 20%) activation, it appears likely that foreign compounds can activate epoxide hydrolase in man.
迄今为止，环氧水解酶（环氧化物水化酶、环氧水解酶，E.C. 3.3.2.3）的活性仅在亚细胞制剂中进行过测定。我们在此表明，对于高度亲脂性底物（3H）-苯并（a）芘4,5-氧化物，该活性可在完整细胞中测定。完整的人淋巴细胞对其水解的速率与淋巴细胞匀浆中的水解速率相似。我们之前曾报道，在含有5,6-苯并黄酮的培养基中培养淋巴细胞会导致环氧水解酶活性增加。我们现在证明这种刺激是由于酶的激活，并且酶的诱导在任何可测量的程度上都不会导致这种增加。此外，5,6-苯并黄酮和7,8-苯并黄酮均可激活环氧水解酶。这种激活不仅发生在细胞匀浆中，而且在完整淋巴细胞中也会发生，且具有相似的浓度-反应关系。因此，在亚细胞制剂中测定环氧水解酶活性反映了这些完整细胞中的活性。此外，由于1微摩尔浓度的苯并黄酮足以引起可测量的（10%至20%）激活，因此外来化合物似乎有可能在人体内激活环氧水解酶。
