Ru(II)-diimine labeled P450 mutants for the selective hydroxylation of substrate

描述（由申请人提供）：细胞色素P450是血红素硫酸酯单加氧酶的超家族，几乎存在于所有生物体中，在内源性化合物的生物合成和生物降解中起重要作用。在人类中，p450酶是参与药物代谢和生物活化的主要酶，占总代谢的75%。经典的P450反应是将氧原子从氧分子中引入底物非活性炭中心。其机制涉及铁中心O-O键的还原断裂，导致形成一种高度氧化的血红素自由基铁基物质，即化合物i。大多数P450单加氧酶的特点是活性低，稳定性有限，需要昂贵的辅助因子（NAD(P)H）来减少血红素铁，并且通常依赖于称为还原酶的辅助电子载体蛋白。我们建议开发一种新的P450系统，该系统将利用光和水作为唯一的氧原子源，在惰性气氛下进行各种底物C-H键的选择性羟基化。该系统将用作人体P450模型，以促进在药物开发过程的早期识别有毒代谢物，并通过产生广泛的羟基化衍生物来实现先导化合物的多样化。该建议的创新部分是用光敏剂Ru（II）二亚胺络合物共价连接到血红素结构域来取代还原酶。然后，活性化合物I将在惰性气氛下，通过光氧化途径直接从酶静止状态下与Fe（III）结合的水产生，而不是通过当前的还原机制。这种方法将能够控制光敏剂和血红素结构域之间的电子流，同时避免由于活性氧而导致蛋白质的快速失活。该系统将导致酶对底物C-H键选择性羟基化的活性增强。

DESCRIPTION (provided by applicant): Cytochromes P450 are a superfamily of heme-thiolate monooxygenases, found in almost all living organisms, that play an important role in the biosynthesis and biodegradation of endogenous compounds. In humans, P450s are the major enzymes involved in drug metabolism and bioactivation, accounting for 75% of the total metabolism. The classical P450 reaction is the introduction of an oxygen atom, derived from molecular oxygen, into a substrate unactivated carbon center. The mechanism involves the reductive scission of the O-O bond at the iron center, leading to the formation of a highly oxidative heme radical ferryl species, namely Compound I. Most P450 monooxygenases are characterized by low activity, limited stability, need of an expensive cofactor (NAD(P)H) to reduce the heme iron and general dependence on auxiliary electron carrier proteins called reductases. We propose to develop a novel P450 system that will utilize light and water as the only source of oxygen atom to perform, under inert atmosphere, the selective hydroxylation of various substrate C-H bonds. This system will be used as a human P450 model to facilitate the identification of toxic metabolites early in the drug development process and to enable the diversification of lead compounds through the generation of a broad range of hydroxylated derivatives. The innovative part of this proposal is to replace the reductase by a photosensitizer Ru(II) diimine complex covalently attached to the heme domain. The reactive Compound I will then be generated, under inert atmosphere, via a photo-oxidative route directly from the water bound to the Fe(III) in the resting state of the enzyme rather than through the current reductive mechanism. This approach will enable the control of the electron flow between the photosensitizer and the heme domain while avoiding the rapid deactivation of the protein due to reactive oxygen species. The proposed system will result in enhanced activity of the enzymes towards the selective hydroxylation of substrate C-H bonds. PUBLIC HEALTH RELEVANCE: This proposal aims at developing a novel biocatalyst to selectively insert an oxygen atom into a substrate C-H bond using visible light and water, under inert atmosphere. This system will be used as an innovative model of human P450 enzymes, which are responsible for the bioactivation and biodegradation of 75% of all drugs.