相容性溶质四氢嘧啶(Ectoine)及衍生物5-羟基四氢嘧啶(5-hydroxyectoine，HE)具有保护蛋白质、核酸等生物大分子甚至细胞的作用，是生物医学和生物制剂的研发热点。HE对极端条件的抵抗性优于Ectoine，其羟基化反应由Ectoine羟基化酶(EctD)催化完成。EctD是一类非血红素依赖的铁氧合酶，该酶反应除需底物以外，还需共底物α-酮戊二酸和氧气的参与，并与酶中心Fe共同形成八面体配合物。目前，关于Ectoine羟化反应可能的底物结合方式、具体攫氢位置和电子转移途径等酶促反应机制，尚不明确。本研究以底物Ectoine的立体异构体及类似物作为假底物，探讨酶EctD与底物的结合方式、攫氢位置及其产物的立体结构，从而明确底物与活性中心Fe(II)及周围氨基酸的互作及空间位置取向，为进一步阐明EctD的催化机制以及实现体外酶化学合成，提供一定的理论支持和技术参考。

Ectoine and hydroxyectoine are important osmotic solutes, they also serve as a protectant for biomacromolecules like proteins, nucleic acid as well as whole cell. Hydroxyectoine is more effective than ectoine when confront extreme conditions, therefore, it was booming in biomedical and biologics. Ectoine hydroxylase (EctD), a non-heme iron dioxgenase, is responsible for converting ectoine to hydroxyectoine. Except for ectoine, α-keto glutarate and oxygen are also required for this reaction to form the classic octahedral complexes together with ferrous. Currently the position of ectoine within the complex and how it binds with the octahedral complex in the reaction is still unclear. Therefore, in order to investigate the mechanism involved in the reaction of EctD and ectoine, serval pseduosubstrates are designed and synthesized to validate the binding type between EctD and substrate, the accurate site of extracting hydrogen from substrate and the exact structure of product. This study will help to elucidate the catalytic mechanism of EctD, and afford theory and technique about achieving plenty of HE by enzyme catalyzed in vitro.