Heinemeyer E A, Geis M, Richter D
Eur J Biochem. 1978 Aug 15;89(1):125-31. doi: 10.1111/j.1432-1033.1978.tb20904.x.
Guanosine 3'-diphosphate 5'-diphosphate (ppGpp) is rapidly degraded to guanosine 5'-diphosphate (ppG) and probably pyrophosphate by an enzyme present in the ribosomal fraction prepared from spoT+ strains of Escherichia coli. The ppGpp-degrading enzyme was released from the ribosomes during dissociation at low ionic strength. Ribosomes are not essential for degradation of ppGpp, and decay of ppGpp is strictly dependent on manganese ions. The reaction is sensitive to inhibition by tetracycline, which can be reversed by MnCl2, indicating that the inhibitory effect is due to the previously described chelating properties of the antibiotic. When the ppGpp-degrading enzyme was complemented with adenosine 5'-triphosphate (pppA) and a nucleoside diphosphate kinase, decay of ppGpp was accelerated yielding pppG and ppG as major products. In the absence of pppA we have been unable to detect the ppGpp-degrading enzyme in various spoT- mutant strains indicating that this enzyme is the spoT gene product.
鸟苷3'-二磷酸5'-二磷酸（ppGpp）可被从大肠杆菌spoT⁺菌株制备的核糖体组分中存在的一种酶迅速降解为鸟苷5'-二磷酸（ppG），可能还有焦磷酸。在低离子强度下解离过程中，ppGpp降解酶从核糖体上释放出来。核糖体对于ppGpp的降解并非必不可少，且ppGpp的降解严格依赖于锰离子。该反应对四环素抑制敏感，而氯化锰可逆转这种抑制，这表明抑制作用是由于该抗生素先前所述的螯合特性。当ppGpp降解酶与腺苷5'-三磷酸（pppA）和核苷二磷酸激酶互补时，ppGpp的降解加速，产生pppG和ppG作为主要产物。在没有pppA的情况下，我们无法在各种spoT⁻突变菌株中检测到ppGpp降解酶，这表明该酶是spoT基因的产物。
