PDF(Pubmed)
Abstract：
During growth, bacteria remodel and recycle their peptidoglycan (PG). A key family of PG-degrading enzymes is the lytic transglycosylases, which produce anhydromuropeptides, a modification that caps the PG chains and contributes to bacterial virulence. Previously, it was reported that the polar-growing Gram-negative plant pathogen Agrobacterium tumefaciens lacks anhydromuropeptides. Here, we report the identification of an enzyme, MdaA (MurNAc deacetylase A), which specifically removes the acetyl group from anhydromuropeptide chain termini in A. tumefaciens, resolving this apparent anomaly. A. tumefaciens lacking MdaA accumulates canonical anhydromuropeptides, whereas MdaA was able to deacetylate anhydro-N-acetyl muramic acid in purified sacculi that lack this modification. As for other PG deacetylases, MdaA belongs to the CE4 family of carbohydrate esterases but harbors an unusual Cys residue in its active site. MdaA is conserved in other polar-growing bacteria, suggesting a possible link between PG chain terminus deacetylation and polar growth.
摘要：
在成长过程中,细菌重塑和回收它们的肽聚糖。肽聚糖降解酶的关键家族是裂解转糖基转移酶，产生脱水莫罗肽，一种修饰，覆盖肽聚糖链并有助于细菌毒力。以前有报道说，极性生长的革兰氏阴性植物病原体根癌农杆菌缺乏脱水莫罗肽。这里,我们报告了一种酶的鉴定，Mdaa,它能特异性地从根癌农杆菌的脱水莫罗肽链末端去除乙酰基，解决这个明显的异常。A.缺乏MdaA的根癌会积累典型的脱水莫罗肽，而MdaA能够在缺乏这种修饰的纯化囊中对脱水N-乙酰基胞壁酸进行脱乙酰。至于其他肽聚糖脱乙酰酶，MdaA属于碳水化合物酯酶的CE4家族，但在其活性位点具有不寻常的Cys残基。MdaA在其他极地生长的细菌中保守，提示肽聚糖链末端去乙酰化与极性生长之间可能存在联系。
