Yoshino M, Tsukada T, Murakami K, Tsushima K
Arch Microbiol. 1980 Dec;128(2):222-7. doi: 10.1007/BF00406162.
AMP-degrading pathways in Azotobacter vinelandii cells were investigated. AMP nucleosidase (EC 3.2.2.4) was rapidly synthesized and reached a maximum at 24 h, while the activity of 5'-nucleotidase (EC 3.1.3.5) specific for AMP, which was negligible during the logarithmic phase of the growth, first appeared in 24 h-cultures, and reached a maximum after complete exhaustion of sucrose from the growth medium (70 h). Cell-free extracts of A. vinelandii of 48 h-cultures hydrolyzed AMP to ribose 5-phosphate and adenine in the presence of ATP, and adenine was deaminated to hypoxanthine. When ATP was excluded, AMP was dephosphorylated to adenosine, which was further metabolized to inosine, and finally to hypoxanthine. Hypoxanthine thus formed was reutilized for the salvage synthesis of IMP under the conditions where 5-phosphoribosyl 1-pyrophosphate was able to be supplied. These results suggest that the levels of ATP can determine the rate of AMP degradation by the AMP nucleosidase- and 5-'nucleotidase-pathways. The role of ATP in the AMP degradation was discussed in relation to the regulatory properties of AMP nucleosidase, inosine nucleosidase (EC. 3.2.2.2) and adenosine deaminase (EC 3.5.4.4).
对棕色固氮菌细胞中的AMP降解途径进行了研究。AMP核苷酶（EC 3.2.2.4）迅速合成，并在24小时达到最大值，而对AMP具有特异性的5'-核苷酸酶（EC 3.1.3.5）的活性在生长对数期可忽略不计，在培养24小时的培养物中首次出现，并在生长培养基中的蔗糖完全耗尽后（70小时）达到最大值。48小时培养的棕色固氮菌的无细胞提取物在ATP存在下将AMP水解为5-磷酸核糖和腺嘌呤，腺嘌呤脱氨生成次黄嘌呤。当排除ATP时，AMP去磷酸化生成腺苷，腺苷进一步代谢生成肌苷，最终生成次黄嘌呤。在能够提供5-磷酸核糖-1-焦磷酸的条件下，如此形成的次黄嘌呤被重新用于IMP的补救合成。这些结果表明，ATP水平可以决定AMP核苷酶和5'-核苷酸酶途径对AMP的降解速率。结合AMP核苷酶、肌苷核苷酶（EC. 3.2.2.2）和腺苷脱氨酶（EC 3.5.4.4）的调节特性，讨论了ATP在AMP降解中的作用。
