CYP3A各亚型间在氨基酸序列、组织分布、配体特异性等方面具有定性层面的高度相似性。但由于3A5易受基因多态性影响，且3A4和3A5对某些治疗窗狭窄药物的偏好性不同，在某些组织或病理条件下，3A亚型的贡献率会呈现定量层面的显著差异，直接影响药物在个体的有效性和安全性。目前3A4和3A5亚型间的差异机制仍不清楚，且缺乏具有临床意义的有效区分方法。本项目借助前期获得的多种亚型高选择性配体，以典型代表性配体：木脂素类、甾体类等作为模式化合物，拟通过体外代谢/抑制实验、联合分子动力学模拟和定点突变技术，开展系列模式化合物与3A亚型的相互作用研究，定性定量评价和比较酶大分子和配体小分子双方面结构差异对3A4和3A5两亚型与配体识别、结合和催化行为差异的影响，深入揭示3A亚型与配体相互作用差异的分子机制。为理性设计和开发属性优良的3A亚型高选择性配体分子并服务于临床的个性化精准医疗提供理论依据和基础。

CYP3A isoforms have similar qualitative characteristics: possess high similarity in the amino acids sequences, have similar tissue distribution characteristics and have extensive overlapping ligands specificities. However, the expression of CYP3A5, but not 3A4, is more susceptible to polymorphism, and for some narrow therapeutic index drugs, the quantitative contributions of each 3A isoform were markedly different in some tissues or under the pathological conditions, which directly affect the effectiveness and safety of drugs in individuals. Unfortunately, the mechanistic differences of the isoforms remains unclear and there is still a lack of clinically effective approaches to differentiate the CYP3A isoforms. In this project, we employ the highly isoform-selective ligands that we previously obtained and choose the typical representative ligands such as lignans and steroids as the model compounds. Together, in vitro metabolism/inhibition experiments combined with molecular dynamics simulation and site direct mutant generation will be employed in this project to qualitatively and quantitatively study the effects of structural difference of enzyme and ligand on the recognition, binding and catalytic behaviors between CYP3A isoforms and ligands. Structural and mechanistic insights into the 3A isoforms-ligand interactions could be helpful and useful to design and obtain highly isoform-specific ligands, which detect various activities of 3A isoforms and provide precise guidance for personalized medicine.