Gates M L, Sanders C C, Goering R V, Sanders W E
Antimicrob Agents Chemother. 1986 Sep;30(3):453-7. doi: 10.1128/AAC.30.3.453.
The multiple stages of derepression of the type I chromosomal beta-lactamase in Pseudomonas aeruginosa were examined. Mutants partially and fully derepressed for beta-lactamase were selected from a wild-type clinical isolate. An analysis of the beta-lactamase produced by these mutants and the induced wild type revealed significant differences in the products of derepression at each stage. Beta-lactamase produced by the fully derepressed mutant showed a lower affinity (Km, 0.113 mM) for cephalothin than that produced by the partially derepressed mutant (Km, 0.049 mM). However, due to a very large Vmax, the former possessed a much greater hydrolytic efficiency. Differences in substrate profile were also noted. Only beta-lactamase from the fully derepressed mutant hydrolyzed cefamandole, cefoperazone, and cefonicid. The partially derepressed mutant possessed a single beta-lactamase band with a pI of 8.4. The fully derepressed mutant possessed this band and an additional major band with a pI of 7.5. Induction of the wild type with cefoxitin produced both bands. The changes in physiologic parameters of the enzymes produced in the different stages of derepression suggest a complex system for beta-lactamase expression in P. aeruginosa. This may involve at least two distinct structural regions, each of which is under control of the same repressor.
对铜绿假单胞菌中I型染色体β-内酰胺酶去阻遏的多个阶段进行了研究。从野生型临床分离株中筛选出β-内酰胺酶部分去阻遏和完全去阻遏的突变体。对这些突变体以及诱导的野生型所产生的β-内酰胺酶进行分析，结果显示在每个去阻遏阶段所产生的产物存在显著差异。完全去阻遏突变体产生的β-内酰胺酶对头孢噻吩的亲和力（Km，0.113 mM）低于部分去阻遏突变体产生的β-内酰胺酶（Km，0.049 mM）。然而，由于Vmax非常大，前者具有更高的水解效率。还注意到底物谱存在差异。只有完全去阻遏突变体产生的β-内酰胺酶能够水解头孢孟多、头孢哌酮和头孢尼西。部分去阻遏突变体有一条pI为8.4的单一β-内酰胺酶条带。完全去阻遏突变体有这条条带以及一条额外的主要条带，其pI为7.5。用头孢西丁诱导野生型产生了这两条条带。在去阻遏不同阶段所产生的酶的生理参数变化表明，铜绿假单胞菌中β-内酰胺酶表达存在一个复杂的系统。这可能涉及至少两个不同的结构区域，每个区域都受同一个阻遏物的调控。
