近日来自上海交通大学微生物代谢国家重点实验室的研究人员在新研究中揭示了头孢菌素酰化酶的自剪切分子机制，并证实头孢菌素酰化酶是一个酰化肽酶，并具有一定的外切肽酶活性，还深入探讨了有关弱催化机制与分子内张力的相互关系。相关研究论文在线发表在发表在美国生物化学与分子生物学会会刊《生物化学期刊》（The Journal of Biological Chemistry）上。
领导这一研究的是上海交通大学邓子新院士，其早年毕业于华中农业大学，2005年当选为中国科学院院士。邓子新院士长期从事微生物分子生物学研究，在重要类别抗生素生物合成基因克隆、定位、结构功能分析、表达和遗传调控机制、抗生素代谢工程与药物创新、天然产物的生物化学与组合生物合成等方面取得了系统性研究进展。
在这篇文章中博士研究生殷俊等揭示了头孢菌素酰化酶第二步自剪切是由于分子内相互作用，并由N-端亲和基团（Ntn）催化完成。这一新催化模型的提出预示着在剪切过程中，该酶必须经历一个很大的构象变化，以克服距离约22?的空间障碍。结合晶体学数据，运用高分辨质谱分析技术对头孢菌素酰化酶空间肽的研究，为酶催化的动态机制提供了重要的实验证据。此外，文章还揭示了头孢菌素酰化酶是一个酰化肽酶，并具有一定的外切肽酶活性，深入探讨了有关弱催化机制与分子内张力的相互关系，丰富了酶催化的理论知识。
2011年邓子新院士研究团队在抗生素生物合成和分子酶学研究领域取得了一系列新成果。在今年3月发表在同一期刊的论文中，博士研究生黄婷婷等运用现代分子生物学与天然产物化学技术，成功克隆了具有显著抗结核分支杆菌活性的抗生素吡啶霉素的生物合成基因簇，通过系统的体内遗传学和体外分子酶学研究阐明了该抗生素生物合成的起始机制，证实了嵌合在非核糖体合成酶中的聚酮还原酶结构域的功能，并推测出两个吡啶环的生物合成模型。在此基础上运用前体导向的生物合成技术，获得了三个新结构吡啶霉素类似物，为成功利用组合生物合成技术产生新结构、新活性的药物或先导化合物奠定了基础。 （生物谷Bioon.com）
生物谷推荐原文：
The Journal of Biological Chemistry DOI：10.1074/jbc.M111.242313
The N-terminal nucleophile serine of cephalosporin acylase executes the second autoproteolytic cleavage and Acyl-peptide hydrolysis
Jun Yin, Zixin Deng, Guoping Zhao and Xi Huang
Cephalosporin acylase precursor is translated as a single polypeptide chain and folds into a self-activating pre-protein. Activation requires two peptide bond cleavages that excise an internal spacer to form the mature αβ heterodimer. Using Q-TOF LC/MS, we located the second cleavage site between E159 and G160, and detected the corresponding 10 aa spacer G160DPPDLADQG169 of CA mutants. The site of the second cleavage depended on E159: moving E into the spacer or removing 5-10 residues from the spacer sequence resulted in shorter spacers with the cleavage at the carboxylic side of E. The mutant E159D was cleaved more slowly than the wild-type CA, as were the two mutants G160A and G160L. This allowed kinetic measurements showing that the second cleavage reaction was a first-order, intra-molecular process. Glutaryl-7-amino-cephalosporanic acid (Gl-7-ACA) is the classic substrate of CA, in which the N-terminal S170 of the β-subunit, is the nucleophile. E and D resemble glutaryl, suggesting that CA might also remove N-terminal E or D from peptides. This was indeed the case, suggesting that the N-terminal nucleophile (Ntn) also performed the second proteolytic cleavage. We also found that CA is an acyl-peptide hydrolase rather than a previously expected acyl-amino acid acylase. It only exhibited exopeptidase activity for the hydrolysis of an externally added peptide, supporting the intra-molecular interaction. We propose that the final CA activation is an intra-molecular process performed by an Ntn mechanism, during which large conformational changes in the α-subunit C-terminal region are required to bridge the gap between E159 and S170.
