REGULATION OF CYTOSOL 5'-NUCLEOTIDASE BY ADENYLATE ENERGY-CHARGE
REGULATION OF CYTOSOL 5'-NUCLEOTIDASE BY ADENYLATE ENERGY-CHARGE
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DOI：
10.1016/0005-2744(81)90268-0
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发表时间：
1981-01-01
期刊：
影响因子：
--
通讯作者：
ITOH, R
中科院分区：
文献类型：
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作者：
ITOH, R
在肝腺苷酸能荷的生理范围内（0.7-0.9），大鼠肝胞液5“-核苷酸酶（5”-核糖核苷酸磷酸水解酶，EC 3.1.3.5）催化AMP水解的速率随能荷的降低而急剧增加。在腺苷酸能荷的生理范围内，Pi浓度的降低引起AMP水解活性的显著加速。这些反应似乎有助于保护细胞免受代谢应激的影响，代谢应激可能是由于去除AMP而突然利用ATP引起的。该酶的AMP水解活性急剧下降的腺嘌呤核苷酸池的大小在生理范围内减少。这种效应可能是一种自限性反应，以防止池的过度消耗。IMP水解活性随腺苷酸能荷的增加而增加。但在生理范围内对它的变化无明显反应。根据本研究中获得的数据，大鼠肝细胞中胞质溶胶5“-核苷酸酶的IMP水解活性似乎与AMP脱氨酶反应的活性相当，但在能荷值约为0.7时，AMP水解活性估计小于AMP脱氨酶反应的10%。这有力地表明AMP →IMP →肌苷途径比AMP途径更重要。腺苷大鼠肝脏肌苷途径
In the physiological range of the adenylate energy charge in liver (0.7-0.9), the rate of AMP-hydrolysis catalyzed by rat liver cytosol 5''-nucleotidase (5''-ribonucleotide phosphohydrolase, EC 3.1.3.5) increased sharply with decreasing energy charge. A decrease in the concentration of Pi caused marked acceleration of the AMP-hydrolyzing activity over the physiological range of adenylate energy charge. These responses seem to serve to protect the cells against a metabolic stress which could result from sudden utilization of ATP by removal of AMP. The AMP-hydrolyzing activity of this enzyme decreased sharply as the size of the adenine nucleotide pool decreased in the physiological range. This effect may be a self-limiting response to prevent excess depletion of the pool. IMP-hydrolyzing activity of this enzyme increased with increasing adenylate energy charge. But no marked response to its variation within the physiological range was observed. On the basis of the data obtained in this study, the IMP-hydrolyzing activity of the cytosol 5''-nucleotidase in rat liver cells seems to be comparable to that of AMP deaminase reaction, but the AMP-hydrolyzing activity was estimated to be less than 10% of AMP deaminase reaction at energy charge value of about 0.7. This strongly suggests that the AMP .fwdarw. IMP .fwdarw. inosine pathway is more significant than the AMP .fwdarw. adenosine .fwdarw. inosine pathway in rat liver.