Sugai M, Fujiwara T, Ohta K, Komatsuzawa H, Ohara M, Suginaka H
Department of Microbiology, Hiroshima University School of Dentistry, Minami-ku, Japan.
J Bacteriol. 1997 Jul;179(13):4311-8. doi: 10.1128/jb.179.13.4311-4318.1997.
Staphylococcus capitis EPK1 produces a glycylglycine endopeptidase, ALE-1 (M. Sugai, T. Fujiwara, T. Akiyama, M. Ohara, H. Komatsuzawa, S. Inoue, and H. Suginaka, J. Bacteriol. 179:1193-1202, 1997), which hydrolyzes interpeptide pentaglycine chains of cell wall peptidoglycan of S. aureus. Characterizations of the enzyme activity and cloning of ale-1 revealed that ALE-1 is very similar to prolysostaphin produced by S. simulans bv. staphylolyticus. Strain EPK1 is resistant to lysis by ALE-1 and by lysostaphin. A gene that renders the cells resistant to glycylglycine endopeptidase (epr) was found 322 bp upstream of and in the opposite orientation to ale-1. The deduced amino acid sequence of epr showed similarities to FemA and FemB, which have been characterized as factors essential for methicillin resistance of S. aureus. Inactivation of either femA or femB causes decreased resistance to methicillin, increased resistance to lysostaphin, and decreased glycine content in the interpeptide chains of peptidoglycan. Therefore, femAB is suggested to be involved in the addition of glycine to pentapeptide peptidoglycan precursor. S. aureus with epr on a multicopy plasmid had phenotypes similar to those of femAB mutants except that it did not alter resistance level to methicillin. These results suggest that epr and femAB belong to the protein family involved in adding amino acids to the pentapeptide peptidoglycan precursor and that epr is involved in the addition of serine to the pentapeptide.
头状葡萄球菌EPK1产生一种甘氨酰甘氨酸内肽酶ALE-1（M. 菅井、藤原隆、秋山智、大原真、小泽秀、井上伸、杉中秀，《细菌学杂志》179:1193 - 1202，1997），该酶可水解金黄色葡萄球菌细胞壁肽聚糖的肽间五甘氨酸链。对该酶活性的表征及ale-1的克隆表明，ALE-1与模仿葡萄球菌溶菌亚种产生的原溶葡萄球菌素非常相似。菌株EPK1对ALE-1和溶葡萄球菌素的裂解具有抗性。在ale-1上游322 bp处发现了一个使细胞对甘氨酰甘氨酸内肽酶产生抗性的基因（epr），且其方向相反。epr推导的氨基酸序列与FemA和FemB相似，FemA和FemB已被鉴定为金黄色葡萄球菌耐甲氧西林的必需因子。femA或femB的失活会导致对甲氧西林的抗性降低、对溶葡萄球菌素的抗性增加以及肽聚糖肽间链中甘氨酸含量降低。因此，推测femAB参与了五肽肽聚糖前体中甘氨酸的添加。携带多拷贝质粒上epr的金黄色葡萄球菌具有与femAB突变体相似的表型，只是其对甲氧西林的抗性水平没有改变。这些结果表明，epr和femAB属于参与向五肽肽聚糖前体添加氨基酸的蛋白质家族，且epr参与了向五肽中添加丝氨酸的过程。
