Krebs H A, Wiggins D
Biochem J. 1978 Jul 15;174(1):297-301. doi: 10.1042/bj1740297.
The origin of the GTP needed for th phosphorylation of AMP in the mitochondrial matrix was investigated. When short-chain fatty acids are metabolized by hepatocytes, AMP is readily formed within the matrix by the butyryl-CoA ligase (AMP-forming) reaction (EC 6.2.1.2). The rate of matrix AMP formation in rat hepatocytes was calculated from the rate of ketone-body formation. The rate of the reconversion of matrix AMP into ADP by GTP-AMP transphosphorylase is limited by the rate of supply of GTP. GTP can be formed either by succinic thiokinase (EC 6.2.1.4) or by nucleoside diphosphokinase (EC 2.7.4.6). The rate of the succinic thiokinase reaction was calculated from turnover of the tricarboxylic acid cycle and this was calculated from the rate of O2 consumption and ketone-body formation. The results show that nucleoside diphosphokinase can make a major contribution (up to 80%) to the supply of GTP under the test conditions.
对线粒体基质中AMP磷酸化所需GTP的来源进行了研究。当短链脂肪酸被肝细胞代谢时，AMP可通过丁酰辅酶A连接酶（生成AMP）反应（EC 6.2.1.2）在基质中轻易形成。大鼠肝细胞中基质AMP的生成速率由酮体生成速率计算得出。GTP-AMP转磷酸化酶将基质AMP再转化为ADP的速率受GTP供应速率的限制。GTP可由琥珀酰硫激酶（EC 6.2.1.4）或核苷二磷酸激酶（EC 2.7.4.6）生成。根据三羧酸循环的周转率计算琥珀酰硫激酶反应的速率，而三羧酸循环的周转率则根据氧气消耗速率和酮体生成速率计算得出。结果表明，在测试条件下，核苷二磷酸激酶对GTP的供应可做出主要贡献（高达80%）。
