Studies on Nucleophilic Cysteine Enzymes Involved in Bacterial Cell Wall Biosynthesis

b -内酰胺类抗生素是应用最广泛的一类抗生素，通过抑制细菌细胞壁的合成而起作用。然而，随着这类抗生素耐药性水平的提高，我们不能再依靠它们治疗常见传染病的能力。L， d -转肽酶（Ldts）是参与细菌细胞壁合成的酶，通常不能被b-内酰胺类抗生素有效抑制。Ldts大多具有非必需功能，但例外情况包括结核分枝杆菌LdtMt2，它对毒力至关重要，以及粪肠杆菌Ldtfm，它可导致对b-内酰胺类抗生素产生耐药性。Ldts与其他转肽酶的不同之处在于其催化位点采用亲核半胱氨酸而不是丝氨酸残基。本项目将涉及对Ldts的研究，最初的重点是LdtMt2，以期详细了解它们的机制和结构。该项目将包括质谱、核磁共振、蛋白质晶体学等技术，开发新的检测方法和鉴定潜在的Ldt抑制剂。该研究结果将增加我们对半胱氨酸酶的作用机制的认识，帮助我们深入了解Ldts在细菌生存和抗菌耐药性中的作用，并可能为开发新型的Ldts和其他类型的亲核半胱氨酸酶抑制剂开辟道路。

B-Lactam antibiotics are the most widely used class of antibiotics, acting through the inhibition of the bacterial cell wall synthesis. However, with increasing levels of resistance for this type of antibiotics we can no longer rely on their ability to treat common infectious diseases. L,D-transpeptidases (Ldts) are enzymes involved in bacterial cell wall synthesis that are generally not effectively inhibited by b-lactam antibiotics. The Ldts possess mostly non-essential functions, but exceptions include the M. tuberculosis LdtMt2 which is essential for virulence, and the E. faecium Ldtfm which can lead to resistance for b-lactam antibiotics. Ldts differ from other transpeptidase enzymes by employing a nucleophilic cysteine rather than a serine residue in its catalytic site. This project will involve studies on Ldts, initially focusing on LdtMt2, with a view to understanding their mechanisms and structures in detail. The project will include techniques such as MS, NMR, protein crystallography, the development of novel assays and the identification of potential Ldt inhibitors. The overall results will increase our understanding on the mechanism of cysteine enzymes and help us gain insight into the function Ldts play in bacterial survival and antibacterial resistance and may open the way to new types of inhibitors of Ldts and other classes of nucleophilic cysteine enzymes.