Daumy G O, Danley D, McColl A S, Apostolakos D, Vinick F J
J Bacteriol. 1985 Sep;163(3):925-32. doi: 10.1128/jb.163.3.925-932.1985.
Proteus rettgeri and Escherichia coli W were shown to express structurally different penicillin G acylases. The enzymes had similar substrate specificity but differed in molecular weight, isoelectric point, and electrophoretic mobility in polyacrylamide gels and did not antigenically cross-react. When the organisms were subjected to environmental conditions which made expression of this enzyme essential for growth, spontaneous mutants were isolated that used different amides as the only source of nitrogen. These mutants acquired the ability to use amides for growth by deregulating the penicillin G acylase and by their evolution to novel substrate specificities. The enzymes expressed by mutants isolated from each genus appeared to have evolved in parallel since each acylase attained similar new substrate specificities when the organisms were subjected to identical selection pressure.
奇异变形杆菌和大肠杆菌W被证明表达结构不同的青霉素G酰化酶。这些酶具有相似的底物特异性，但分子量、等电点和在聚丙烯酰胺凝胶中的电泳迁移率不同，并且在抗原上不会发生交叉反应。当这些生物体处于使该酶的表达对生长至关重要的环境条件下时，分离出了自发突变体，这些突变体使用不同的酰胺作为唯一的氮源。这些突变体通过解除青霉素G酰化酶的调控以及进化出新型底物特异性而获得了利用酰胺进行生长的能力。从每个属中分离出的突变体所表达的酶似乎是平行进化的，因为当生物体受到相同的选择压力时，每种酰化酶都获得了相似的新底物特异性。
