Structure-Function Relationships of Food-Related Proteins/Enzymes: Aspartic Proteinases

我们NSERC资助的研究项目的长期目标是在基本的分子水平上阐明和完善与食物相关的蛋白质（特别是酶）的结构-功能关系（SFRs）的本质。我们的工作重点是天冬氨酸蛋白酶（APs），肽酶A1家族的酶。虽然大多数ap符合某些特征（活性的最佳pH值，作用机制，结构相似性），但也存在差异（稳定性，靶标偏好，翻译后修饰，生物学功能），使ap成为SFR研究的优秀模型。在食品领域，APs作为加工助剂在各种产品的生产中发挥着重要作用，例如，在奶酪的生产中，凝乳酶被用于凝固牛奶。此外，APs是食品植物保护的一部分（如大麦、番茄、土豆），有些对食品病原体（如有毒的芽孢杆菌和葡萄球菌）有活性。因此，ap对食品安全和供应至关重要。了解AP的生物化学不仅对食品相关的过程/问题很重要，而且AP SFR知识也与代谢功能（调节血压）和疾病状态（疟疾，艾滋病）相关。该研究将继续使用蛋白质工程和物理化学技术的结合来检查APs的SFRs，以促进三个主要领域的知识现状：(I)蛋白质折叠过程，（II）植物AP抗病原体结构域SFRs，以及（III）不同来源APs的相似性/差异性。蛋白质折叠将通过确定称为前片段的特定AP部分如何影响蛋白质折叠/展开来研究。抗病原体AP结构域将在它们与膜的相互作用以及它们在AP酶功能中的作用方面进行研究。研究ap的相似性/差异性将集中在表现出极端行为的ap上，包括在高温下的功能以及在异常pH值下的酶稳定性。通过回答基本的、假设驱动的问题，这些研究无疑将有助于更有效地使用、控制和设计具有所需功能的与食物相关的蛋白质/酶。

The long-term goal of our NSERC funded research program has been to elucidate and refine the nature of structure-function relationships (SFRs) of food-related proteins (particularly enzymes) at a fundamental, molecular level. Our work focuses on aspartic proteinases (APs), the Peptidase A1 family of enzymes. While most APs conform to certain characteristics (optimum pH for activity, mechanism of action, structural similarity), there are differences (stability, target preference, post-translational modification, biological function) that make APs an excellent model for SFR studies. In the food area, APs play prominent roles as processing aids in the manufacture of a variety of products, e.g., chymosin is used to coagulate milk in the production of cheese. Additionally, APs are part of food plant protection (e.g., barley, tomato, potato), and some are active against food pathogens (e.g., toxic Bacillus and Staphylococcus species). Thus, APs are critical to food safety and supply. Understanding the biochemistry of APs is not only important for food-related processes/issues, but AP SFR knowledge is also relevant in metabolic functions (regulating blood pressure) and in disease states (malaria, AIDS). The proposed research will continue to examine SFRs of APs using a combination of protein engineering and physicochemical techniques to contribute to the current state of knowledge in the three principal areas of (I) protein folding processes, (II) plant AP anti-pathogen domain SFRs, and (III) the similarity/dissimilarity of APs from varied sources. Protein folding will be studied by determining how particular AP portions termed prosegments affect protein folding/unfolding. Anti-pathogen AP domains will be investigated in terms of their interactions with membranes as well as their roles for AP enzymatic functioning. Studying the similarity/dissimilarity of APs will be centred on APs that display extreme behaviour including functioning at high temperatures as well as enzyme stability at unusual pH values. By answering fundamental, hypothesis-driven questions, these studies will undoubtedly aid in the more efficient use, control and design of food-related proteins/enzymes with desired functions.