Satishchandran C, Boyle S M
J Bacteriol. 1984 Feb;157(2):552-9. doi: 10.1128/jb.157.2.552-559.1984.
The putrescine biosynthetic enzyme agmatine ureohydrolase (AUH) (agmatinase; EC 3.5.3.11) catalyzes the conversion of agmatine to putrescine in Escherichia coli. The specific activity of AUH was determined in crude extracts prepared from wild-type strains and from strains with mutations in the adenylate cyclase gene (cya) or the cAMP receptor protein gene (crp) or both. In glucose minimal medium, a delta cya strain exhibited 70 to 90% higher AUH activity than a cya+ strain. Addition of 1 to 10 mM cAMP to cya+ and delta cya strains cultured in glucose repressed AUH activity in a dose-dependent manner. Addition of 1 to 10 mM cAMP to a delta crp strain failed to repress AUH activity. Addition of agmatine resulted in a three- to fourfold induction of AUH in delta cya and delta crp strains. This induction could be blocked by the addition of chloramphenicol. Simultaneous additions of various proportions of cAMP and agmatine resulted in reduced levels of induction and repression of AUH activity. This antagonistic regulation was shown to be exerted by independent mechanisms since AUH activity could be induced by agmatine in a delta crp strain supplemented with cAMP. These results suggest that both agmatine and cAMP antagonistically regulate AUH activity at the level of transcription. In minimal medium supplemented with 1 mM putrescine, the strains did not exhibit repression of AUH activity. In contrast, in minimal medium supplemented with 1 mM ornithine or arginine, cya+ or delta cya strains exhibited induced AUH activity as a result of conversion of these substrates to agmatine. Further experiments in vitro demonstrated that the effects observed with cAMP, agmatine, and arginine were not post-translationally mediated.
腐胺生物合成酶胍丁胺脲水解酶(AUH)(胍丁胺酶;EC 3.5.3.11)在大肠杆菌中催化胍丁胺转化为腐胺。在从野生型菌株以及腺苷酸环化酶基因(cya)或cAMP受体蛋白基因(crp)或两者均发生突变的菌株制备的粗提物中测定了AUH的比活性。在葡萄糖基本培养基中,cya缺失菌株的AUH活性比cya+菌株高70%至90%。向在葡萄糖中培养的cya+和cya缺失菌株中添加1至10 mM的cAMP会以剂量依赖的方式抑制AUH活性。向crp缺失菌株中添加1至10 mM的cAMP未能抑制AUH活性。添加胍丁胺会导致cya缺失和crp缺失菌株中AUH的诱导增加三到四倍。这种诱导可通过添加氯霉素来阻断。同时添加不同比例的cAMP和胍丁胺会导致AUH活性的诱导和抑制水平降低。这种拮抗调节被证明是由独立机制发挥作用的,因为在补充有cAMP的crp缺失菌株中,胍丁胺可诱导AUH活性。这些结果表明,胍丁胺和cAMP在转录水平上对AUH活性进行拮抗调节。在补充有1 mM腐胺的基本培养基中,这些菌株未表现出AUH活性的抑制。相反,在补充有1 mM鸟氨酸或精氨酸的基本培养基中,cya+或cya缺失菌株由于这些底物转化为胍丁胺而表现出诱导的AUH活性。进一步的体外实验表明,观察到的cAMP、胍丁胺和精氨酸的作用不是翻译后介导