INRA, UMR1319 Micalis, F-78350 Jouy-en-Josas, France.
J Biol Chem. 2011 Jul 8;286(27):23950-8. doi: 10.1074/jbc.M111.241414. Epub 2011 May 17.
Peptidoglycan (PG) N-acetyl muramic acid (MurNAc) O-acetylation is widely spread in gram-positive bacteria and is generally associated with resistance against lysozyme and endogenous autolysins. We report here the presence of O-acetylation on N-acetylglucosamine (GlcNAc) in Lactobacillus plantarum PG. This modification of glycan strands was never described in bacteria. Fine structural characterization of acetylated muropeptides released from L. plantarum PG demonstrated that both MurNAc and GlcNAc are O-acetylated in this species. These two PG post-modifications rely on two dedicated O-acetyltransferase encoding genes, named oatA and oatB, respectively. By analyzing the resistance to cell wall hydrolysis of mutant strains, we showed that GlcNAc O-acetylation inhibits N-acetylglucosaminidase Acm2, the major L. plantarum autolysin. In this bacterial species, inactivation of oatA, encoding MurNAc O-acetyltransferase, resulted in marked sensitivity to lysozyme. Moreover, MurNAc over-O-acetylation was shown to activate autolysis through the putative N-acetylmuramoyl-L-alanine amidase LytH enzyme. Our data indicate that in L. plantarum, two different O-acetyltransferases play original and antagonistic roles in the modulation of the activity of endogenous autolysins.
肽聚糖 (PG) N-乙酰基胞壁酸 (MurNAc) O-乙酰化广泛存在于革兰氏阳性菌中，通常与抗溶菌酶和内源性自溶素有关。我们在这里报告了植物乳杆菌 PG 中 N-乙酰葡萄糖胺 (GlcNAc) 的 O-乙酰化。这种糖链的修饰在细菌中从未被描述过。从植物乳杆菌 PG 释放的乙酰化肽聚糖的精细结构特征表明，该物种中的 MurNAc 和 GlcNAc 都被 O-乙酰化。这两种 PG 后修饰依赖于两个分别命名为 oatA 和 oatB 的专用 O-乙酰基转移酶编码基因。通过分析突变菌株对细胞壁水解的抗性，我们表明 GlcNAc O-乙酰化抑制了 N-乙酰葡萄糖胺酶 Acm2，这是植物乳杆菌的主要自溶素。在这种细菌中，编码 MurNAc O-乙酰基转移酶的 oatA 的失活导致对溶菌酶的敏感性显著增加。此外，MurNAc 的过度 O-乙酰化被证明通过假定的 N-乙酰胞壁酰-L-丙氨酸酰胺酶 LytH 酶激活自溶。我们的数据表明，在植物乳杆菌中，两种不同的 O-乙酰基转移酶在调节内源性自溶素的活性方面发挥了原始和拮抗的作用。
