Enzymatic Hydrolysis of Trehalose Dimycolate Releases Free Mycolic Acids during Mycobacterial Growth in Biofilms
Enzymatic Hydrolysis of Trehalose Dimycolate Releases Free Mycolic Acids during Mycobacterial Growth in Biofilms
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DOI：
10.1074/jbc.m110.112813
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发表时间：
2010-06-04
影响因子：
4.8
通讯作者：
Hatfull, Graham F.
中科院分区：
文献类型：
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作者：
Ojha, Anil K.;Trivelli, Xavier;Hatfull, Graham F.
与其他微生物一样，分枝杆菌在体外无洗涤剂液体培养基中生长时，会自发形成多细胞耐药生物膜。结核分枝杆菌生物膜的结构是通过基因编程途径形成的，并建立在大量新的细胞外游离霉菌酸（FM）的基础上，尽管FM合成的机制尚不清楚。在这里，我们发现耻垢分枝杆菌生物膜中的FM是通过酶促释放产生的，这些酶促释放是由组成性存在的霉菌基衍生物产生的。FM的前体之一是新合成的海藻糖二mycolate (TDM)，它被一种新的TDM特异性丝氨酸酯酶Msmeg_1529裂解。mmsmeg_1529的破坏导致无法检测到水解活性，突变体中FM水平降低，生物膜生长迟缓。此外，TDM的酶解在结核分枝杆菌中保持保守，表明该病原体中存在TDM特异性酯酶。总的来说，这项研究提供了分枝杆菌生长过程中游离菌酸从细胞包膜菌酸中酶释放的第一个证据。
Mycobacterial species, like other microbes, spontaneously form multicellular drug-tolerant biofilms when grown in vitro in detergent-free liquid media. The structure of Mycobacterium tuberculosis biofilms is formed through genetically programmed pathways and is built upon a large abundance of novel extracellular free mycolic acids (FM), although the mechanism of FM synthesis remained unclear. Here we show that the FM in Mycobacterium smegmatis biofilms is produced through the enzymatic release from constitutively present mycolyl derivatives. One of the precursors for FM is newly synthesized trehalose dimycolate (TDM), which is cleaved by a novel TDM-specific serine esterase, Msmeg_1529. Disruption of Msmeg_1529 leads to undetectable hydrolytic activity, reduced levels of FM in the mutant, and retarded biofilm growth. Furthermore, enzymatic hydrolysis of TDM remains conserved in M. tuberculosis, suggesting the presence of a TDM-specific esterase in this pathogen. Overall, this study provides the first evidence for an enzymatic release of free mycolic acids from cell envelope mycolates during mycobacterial growth.