Function of Carboxypeptidase D

描述(申请人提供)：羧基肽酶D(CPD)被认为在通过分泌途径的蛋白质的生物合成途径中发挥作用，如胰岛素样生长因子和胰岛素受体。此外，CPD还(与羧基肽酶E一起)参与胰岛素等神经内分泌肽的加工。为了进一步研究CPD的功能，出于几个原因，我们将我们的实验系统从牛、大鼠和鸭子转移到了果蝇的系统。首先，对果蝇CPD和哺乳动物CPD的序列和酶性质的比较反映了进化过程中保守的关键元件。其次，有几个果蝇的CPD突变体(称为Silver，或SVR突变体)存在CPD缺陷，这为检测CPD各个结构域的功能提供了一个方便的体内系统。 其具体目的是：(1)研究果蝇CPD的性质和分布；(2)确定SVR突变体的分子基础以及这些突变对CPD表达和酶性质的影响；(3)通过在SVR突变体中表达特定形式来确定CPD不同结构域的功能；以及(4)检测各种CPD突变体(以及具有特定形式CPD的转基因果蝇)对多肽和蛋白质加工的影响。 综上所述，这些研究将提供对CPD生物学作用的理解。果蝇和哺乳动物之间CPD的高度保守性表明CPD的基本结构域结构对其功能至关重要。这项建议的总体目标是利用一个简单的有机体了解CPD中每个结构域的作用，CPD突变体对其存在，并且可以进行转基因分析。

DESCRIPTION (provided by applicant): Carboxypeptidase D (CPD) is thought to function in the biosynthetic pathway of proteins that transit the secretory pathway, such as insulin-like growth factor and the insulin receptor. In addition, CPD also participates (along with carboxypeptidase E) in the processing of neuroendocrine peptides such as insulin. To further study the function of CPD, we have shifted our experimental system from bovine, rat, and duck to that of Drosophila for several reasons. First, a comparison of the sequence and enzymatic properties of Drosophila CPD with those of mammalian CPD provides a reflection of the key elements that have been conserved through evolution. Second, there are several Drosophila mutants with defects in CPD (named silver, or svr mutants); these provide a convenient in vivo system to test the function of the various domains of CPD. The Specific Aims are: (1) To study the properties and distribution of Drosophila CPD; (2) To determine the molecular basis of the svr mutants and the consequence of these mutations on the expression and enzymatic properties of CPD; (3) To determine the function of the different domains of CPD by expressing specific forms in the svr mutants; and (4) To examine the consequences of the various CPD mutants (and transgenic flies with specific forms of CPD) on the processing of peptides and proteins. Taken together, these studies will provide an understanding of the biological role of CPD. The high degree of conservation of CPD between Drosophila and mammals suggests that the basic domain structure of CPD is critical for its function. The overall goal of this proposal is to understand the role of each domain within CPD, using a simple organism for which CPD mutants exist and which is amenable to transgenic analysis.