Ac-muramic acid (N-acetylmuramic acid, MurNAc) is a ubiquitous bacterial cell wall sugar that carries a unique D-lactyl ether substituent at the C3 position [1]. Ac-muramic acid was used as a substrate for Ac-muramic acid etherase MurQ [1]. Ac-muramic acid was obtained either from the environment or from the endogenous cell wall (i.e., recycling). High-level expression of MurQ is required for growth on Ac-muramic acid as the sole source of carbon and energy, whereas constitutive low-level expression of MurQ is sufficient for the recycling of peptidoglycan fragments continuously released from the cell wall during bacterial growth [2].
In vitro, Ac-muramic acid (0-300μg/mL) concentration-dependently inhibited the iNOS and COX-2 protein and mRNA expression in RAW 264.7 cells [3].
In vivo, Ac-muramic acid (40mg/kg; oral gavage; 25 days) inhibited the intestinal villi edema in the E. coli-induced ICR mice and decreased the production of IFN-α in the blood [3].
References:
[1] Jaeger, Tina, Momo Arsic, and Christoph Mayer. "Scission of the lactyl ether bond of N-acetylmuramic acid by Escherichia coli “etherase”." Journal of Biological Chemistry 280.34 (2005): 30100-30106.
[2] Jaeger, Tina, and Christoph Mayer. "The transcriptional factors MurR and catabolite activator protein regulate N-acetylmuramic acid catabolism in Escherichia coli." Journal of bacteriology 190.20 (2008): 6598-6608.
[3] Wu, Zhen, et al. "N-acetylmuramic acid triggers anti-inflammatory capacity in LPS-induced RAW 264.7 cells and mice." journal of functional foods 13 (2015): 108-116.
Ac-muramic acid (N-acetylmuramic acid, MurNAc) 是一种普遍存在的细菌细胞壁糖，其C3位带有独特的D-乳醚取代基[1]。Ac-muramic acid被用作Ac-muramic acid醚酶MurQ的底物[1]。Ac-muramic acid来源于环境或内源细胞壁（即循环利用）。在以Ac-muramic acid作为唯一碳源和能量来源时，细菌需要高水平表达 MurQ才能维持正常生长，而在细菌生长过程中持续从细胞壁释放的肽聚糖片段的回收，仅需 MurQ的组成型低水平表达即可满足[2]。
在体外，Ac-muramic acid（0-300μg/mL）呈浓度依赖性地抑制RAW 264.7细胞中iNOS和COX-2蛋白及mRNA的表达[3]。
在体内，Ac-muramic acid（40mg/kg；灌胃；25天）抑制大肠杆菌诱导的ICR小鼠肠绒毛水肿，并降低血液中IFN-α水平[3]。