背景：乳酸化修饰作为一种新的翻译后修饰，对于研究蛋白质在生理和病理过程中的功能和调节，以及深入了解包括肿瘤在内的许多疾病的发生和发展是必不可少的。尽管如此，目前对于完整生物体内乳酸化蛋白的研究仍然十分有限。因此，对秀丽隐杆线虫进行全面的蛋白质乳酸化修饰研究，以构建一个体内乳酸化数据库，显得尤为关键。

方法：我们使用成年秀丽隐杆线虫作为研究对象，利用液相色谱串联质谱技术进行实验分析，并通过MaxQuant软件对数据进行定量处理。

结果：采用无标记策略，鉴定了2416个高置信度的蛋白，在487个蛋白中鉴定了1836个高置信度的乳酸化位点。我们的研究还深入探讨了乳酸化修饰在蛋白质二级结构和表面可及性的偏好性，通过非配对Wilcox检验，我们发现位于无规则卷曲结构上的赖氨酸残基更不容易发生乳酸化（P <0.001）。生物信息学分析，我们发现乳酸化蛋白主要集中在细胞质内，并参与三羧酸循环（TCA循环）及其他代谢途径。然后，我们还评估了乳酸化修饰在不同生物体中的保守性，发现秀丽隐杆线虫中总共有41种同源蛋白也在人和大鼠体内被乳酸化。特别值得注意的是，H4K80位点的乳酸化在三个物种中显示出保守性。此外，本研究还首次在秀丽隐杆线虫中鉴定出238个乳酸化蛋白。

结论：本研究首次建立了秀丽隐杆线虫乳酸化数据库和扩展了乳酸化组数据库，为乳酸化的深入研究提供了更有价值的证据。

Background: Lactylation, as a novel posttranslational modification, is essential for studying the functions and regulation of proteins in physiological and pathological processes, as well as for gaining in-depth knowledge on the occurrence and development of many diseases, including tumors. Despite its significance, research on protein lactylation within the whole organism is quite limited. Thus, we studied the lactylation of global proteins in Caenorhabditis elegans to obtain an in vivo lactylome, which is of great importance.

Methods: we used adult Caenorhabditis elegans as study subjects and liquid chromatography tandem mass spectrometry technology was employed for experimental analysis. MaxQuant was used for quantitative analysis.

Results: Using a label-free strategy, we identified 2416 high-confidence proteins and identified 1836 high-confidence lactylated sites in 487 proteins. Our study also explored the preference of lactylation on secondary structure and surface accessibility. Through the unpaired Wilcoxon test, we found that lysine residues located in the random coil structure are less likely to undergo lactylation (P <0.001). Bioinformatics analysis showed that lactylated proteins were mainly located in the cytoplasm and involved in the tricarboxylic acid cycle (TCA cycle) and other metabolic pathways. Then, we evaluated the conservation of lactylation in different organisms. In total, 41 Caenorhabditis elegans proteins were lactylated and homologous to lactylated proteins in humans and rats. Notably, lactylation on H4K80 was conserved in three species. Furthermore, an additional 238 lactylated proteins were identified in Caenorhabditis elegans for the first time.

Conclusion: This study establishes the first atlas of lactylation in Caenorhabditis elegans and expands the lactylome database, providing more valuable evidence for indepth studies of lactylation.