Basu J, Chattopadhyay R, Kundu M, Chakrabarti P
Department of Chemistry, Bose Institute, Calcutta, India.
J Bacteriol. 1992 Jul;174(14):4829-32. doi: 10.1128/jb.174.14.4829-4832.1992.
Penicillin-binding proteins (PBPs), although characterized from several organisms, have so far not been studied in mycobacteria. The present study is the first characterization of a PBP from Mycobacterium smegmatis. The PBP was purified by solubilization of the membranes with Triton X-100 and successive chromatography of the solubilized proteins on ampicillin-linked CH Sepharose 4B and DE-52. The purified PBP (M(r), 49,500) catalyzed a model transpeptidase reaction with the tripeptide acetyl2-L-Lys-D-Ala-D-Ala as the substrate and Gly-Gly as the acceptor. The transpeptidase activity was inhibited by 50% at a benzylpenicillin concentration of 1.8 x 10(-7) M, which was similar to the concentration (1.1 x 10(-7) M) of benzylpenicillin required to saturate to 50% this PBP. Of several antibiotics tested, the concentration of antibiotic required to inhibit [35S]penicillin binding by 90% was found to be the lowest for cefoxitin and Sch 34343.
青霉素结合蛋白（PBPs），尽管已在多种生物体中得到表征，但迄今为止尚未在分枝杆菌中进行研究。本研究是对耻垢分枝杆菌中一种PBP的首次表征。通过用 Triton X - 100溶解细胞膜并将溶解的蛋白质依次在氨苄青霉素连接的CH Sepharose 4B和DE - 52上进行色谱分离来纯化该PBP。纯化的PBP（分子量为49,500）以乙酰基 - 2 - L - 赖氨酸 - D - 丙氨酸 - D - 丙氨酸三肽为底物、甘氨酰 - 甘氨酸为受体催化了一个模型转肽酶反应。在苄青霉素浓度为1.8×10⁻⁷ M时，转肽酶活性被抑制50%，这与使该PBP饱和至50%所需的苄青霉素浓度（1.1×10⁻⁷ M）相似。在测试的几种抗生素中，发现头孢西丁和Sch 34343抑制[³⁵S]青霉素结合90%所需的抗生素浓度最低。
