Wright J M, Boyle S M
Mol Gen Genet. 1982;186(4):482-7. doi: 10.1007/BF00337952.
The polyamine biosynthetic enzymes, ornithine decarboxylase (EC 4.1.1.17) (ODC) and arginine decarboxylase (EC 4.1.1.19) (ADC), are negatively controlled by cAMP in Escherichia coli. The specific activities of ODC and ADC were determined in crude extracts prepared from E. coli strains carrying a mutation in the adenylate cyclase (EC 4.6.1.1) structural gene (cya) and wildtype strains. These strains were cultured on various carbon sources in the presence and absence of cAMP. In wild-type strains, ODC and ADC activities were diminished in cells grown on glycerol compared to these strains cultured on glucose. When cya strains were grown on glucose or glycerol, ODC and ADC activities were the same. Addition of 1 mM cAMP to glucose-based medium repressed ODC and ADC activities in both the wild-type and cya strains. Furthermore, cAMP exerts its negative control through the cAMP receptor protein, since strains carrying a mutation in the crp structural gene fail to repress ODC and ADC activities in response to increased cAMP obtained by carbon source manipulation or cAMP supplementation of the growth medium. This evidence suggests that negative control of ODC and ADC by cAMP occurs at the level of transcription.
多胺生物合成酶，即鸟氨酸脱羧酶（EC 4.1.1.17）（ODC）和精氨酸脱羧酶（EC 4.1.1.19）（ADC），在大肠杆菌中受到cAMP的负调控。ODC和ADC的比活性是在从携带腺苷酸环化酶（EC 4.6.1.1）结构基因（cya）突变的大肠杆菌菌株和野生型菌株制备的粗提物中测定的。这些菌株在有无cAMP的情况下在各种碳源上培养。在野生型菌株中，与在葡萄糖上培养的菌株相比，在甘油上生长的细胞中ODC和ADC活性降低。当cya菌株在葡萄糖或甘油上生长时，ODC和ADC活性相同。向基于葡萄糖的培养基中添加1 mM cAMP会抑制野生型和cya菌株中的ODC和ADC活性。此外，cAMP通过cAMP受体蛋白发挥其负调控作用，因为携带crp结构基因突变的菌株无法响应通过碳源操纵或向生长培养基中添加cAMP而增加的cAMP来抑制ODC和ADC活性。这一证据表明，cAMP对ODC和ADC的负调控发生在转录水平。
