Terminal marking of avian triosephosphate isomerases by deamidation and oxidation.
Terminal marking of avian triosephosphate isomerases by deamidation and oxidation.
复制标题
通过脱酰胺和氧化对禽类磷酸三糖异构酶进行末端标记。
DOI：
10.1006/abbi.1995.1142
复制
发表时间：
1995
期刊：
影响因子：
--
通讯作者：
Gracy,RW
中科院分区：
文献类型：
--
作者：
Zhang,Y;Yuksel,KU;Gracy,RW
磷酸丙糖异构酶(TPI)为末端标记和蛋白质降解提供了一个很好的模型。哺乳动物的TPI通过Asn71-Gly上的脱氨基末端修饰，导致去折叠、解离和蛋白降解。相比之下，鸡肉TPI在71位含有赖氨酸，通过Cys126的氧化而被末端修饰。因此，脱酰胺和氧化都会引发不同物种中TPI的降解。为了探索其他禽类动物的末端标记，我们将火鸡TPI纯化为同源性，并确定了其特性。虽然火鸡和鸡肉TPI的分子性质非常相似，但它们对温度、氧化剂和碱性pH的耐受性却非常不同。例如，鸡TPI在10 mM氧化谷胱甘肽或H_2O_2中都有80%的失活，而120 mM GSSG对火鸡TPI没有影响，需要~gt；120 mM H_2O_2才能使80%失活。在导致哺乳动物TPI迅速去酰胺化的碱性条件下，两种禽酶都不去酰胺化。然而，鸡肉TPI是聚合的。聚集性被2-巯基乙醇逆转。长期暴露在较温和的条件下，火鸡酶在Asn15-Gly时完全失活和去胺化。因此，这两种禽类酶对氧化和脱酰胺的敏感性存在显著差异，它们的末端标记机制似乎也不同。
Triosephosphate isomerase (TPI) provides an excellent model for terminal marking and protein degradation. Mammalian TPI is terminally modified by deamidation at Asn71-Gly, resulting in unfolding, dissociation, and proteolysis. In contrast, chicken TPI, which contains a lysine at position 71, is terminally modified by the oxidation of Cys126. Thus, both deamidation and oxidation initiate degradation of TPI from different species. To explore the terminal marking in other avians, we have purified the turkey TPI to homogeneity and determined its characteristics. Although the molecular properties of the turkey and chicken TPI were very similar, their tolerances to temperature, oxidants, and alkaline pH were very different. For example, chicken TPI was inactivated 80% in either 10 mM oxidized glutathione or H2O2, whereas 120 mM GSSG had no effect on turkey TPI, and >120 mM H2O2was needed for 80% inactivation. Under alkaline conditions that cause rapid deamidation of the mammalian TPI, neither avian enzyme deamidated. Chicken TPI, however, aggregated. Aggregation was reversed by 2-mercaptoethanol. Under prolonged exposure to milder conditions the turkey enzyme was completely inactivated and deamidated at Asn15-Gly. Thus, there are marked differences in the susceptibility of these two avian enzymes to oxidation and deamidation, and their terminal marking mechanisms appear to be different.