Mechanism of digestion of bradykinin and lysylbradykinin (kallidin) in human serum. Role of carboxypeptidase, angiotensin-converting enzyme and determination of final degradation products.
Mechanism of digestion of bradykinin and lysylbradykinin (kallidin) in human serum. Role of carboxypeptidase, angiotensin-converting enzyme and determination of final degradation products.
复制标题
人血清中缓激肽和赖氨缓激肽（激肽）的消化机制。
DOI：
10.1016/0006-2952(89)90290-6
复制
发表时间：
1989
影响因子：
5.8
通讯作者：
Kaplan,AP
中科院分区：
文献类型：
--
作者：
Sheikh,IA;Kaplan,AP
缓激肽和赖氨酰缓激肽的降解在血浆和血清中进行了研究，并与羧肽酶N和血管紧张素转换酶（ACE），两个公认的激酶在血液中的混合物所看到的结果进行了比较。血管紧张素转换酶与生理浓度的羧肽酶N混合后，可将缓激肽消化为二肽Phe-Arg和Ser-Pro加五肽Arg-Pro-Pro-Gly-Phe。羧肽酶N缓慢地从缓激肽中除去C-末端Arg以产生des-Arg 9-缓激肽（DBK）;后者被ACE消化以产生上述五肽和三肽Ser-Pro-Phe。然而，在血清中，C-末端精氨酸从缓激肽中被去除的速度比羧肽酶N的活性快5倍。因此，血清中ACE的主要底物是脱精氨酸缓激肽而不是缓激肽。该反应的产物，五肽和三肽，在血清中是不稳定的，并被切割的酶，尚未得到表征。使用一种产物（游离苯丙氨酸）通过HPLC监测这些反应。我们的研究表明，缓激肽降解的最终产物是三肽Arg-Pro-Pro，一摩尔的Ser，Pro，Gly和Arg，和两摩尔的苯丙氨酸。由于血清中羧肽酶N的水平不能解释激肽的快速降解，其他羧肽酶可能也起作用，可能是由于血液凝固而释放，或者血清辅因子可能增加羧肽酶N的活性。
Degradation of bradykinin and lysylbradykinin was studied in plasma and serum, and the results were compared to those seen with mixtures of carboxypeptidase N and angiotensin-converting enzyme (ACE), the two recognized kininases in blood. Angiotensin-converting enzyme was an effective kininase in mixtures with carboxypeptidase N at physiologic concentration and digested bradykinin to the dipeptides Phe- Arg and Ser-Pro plus the pentapeptide Arg-Pro-Pro-Gly-Phe. Carboxypeptidase N slowly removed the C-terminal Arg from bradykinin to yield des-Arg9-bradykinin (DBK); the latter was digested by ACE to yield the aforementioned pentapeptide and the tripeptide Ser-Pro-Phe. In serum, however, the C-terminal Arg was removed from bradykinin about five times faster than was accounted for by the activity of carboxypeptidase N. The primary substrate of ACE in serum, therefore, was des-Arg9-bradykinin and not bradykinin. The products of this reaction, pentapeptide and tripeptide, were unstable in serum and were cleaved by enzymes that have not yet been characterized. One product, free phenylalanine, was used to monitor these reactions by HPLC. Our studies indicate that the final products of bradykinin degradation were the tripeptide Arg-Pro-Pro, one mole each of Ser, Pro, Gly, and Arg, and two moles of phenylalanine. Since the serum level of carboxypeptidase N did not account for the rapid kinin degradation seen, other carboxypeptidases may have been operative, perhaps released as a result of blood clotting, or a serum cofactor may augment carboxypeptidase N activity.