Kadrmas E F, Ray P D, Lambeth D O
Department of Biochemistry and Molecular Biology, School of Medicine, University of North Dakota, Grand Forks 58202.
Biochim Biophys Acta. 1991 Aug 6;1074(3):339-46. doi: 10.1016/0304-4165(91)90083-s.
The relative abilities of ATP and GTP to support succinyl-CoA synthesis by mitochondrial matrix fractions prepared from rabbit heart and liver mitoplasts were investigated. The activity supported by ATP in rabbit heart preparations was less than 15% of that obtained with GTP, while no ATP-supported activity was observed in rabbit liver preparations. However, the addition of 30 micromolar GDP to matrix fractions from either heart or liver stimulated the ATP-supported activity to 40% of that observed with GTP, and the further addition of bovine liver nucleoside diphosphate kinase in the presence of 8 microM added GDP increased the activity to near that observed with GTP. The specific activity of nucleoside diphosphate kinase assayed directly in mitochondrial matrix from heart was about 15% of the specific activity of ATP-supported succinate thiokinase induced upon adding GDP. Evidence for a complex between nucleoside diphosphate kinase and succinate thiokinase in mitochondrial matrix from rabbit heart was obtained by glycerol density gradient centrifugation. It is proposed that binding of nucleoside diphosphate kinase to succinate thiokinase activates the former enzyme, accounts for the ATP-supported succinyl-CoA synthetase activity observed, and is involved in the channeling of high energy phosphate from GTP produced in the Krebs cycle to the ATP pool.
研究了ATP和GTP支持由兔心脏和肝脏线粒体膜制备的线粒体基质部分合成琥珀酰辅酶A的相对能力。在兔心脏制剂中，ATP支持的活性不到GTP所获活性的15%，而在兔肝脏制剂中未观察到ATP支持的活性。然而，向来自心脏或肝脏的基质部分添加30微摩尔GDP可将ATP支持的活性刺激至GTP所观察到活性的40%，并且在添加8微摩尔GDP的情况下进一步添加牛肝脏核苷二磷酸激酶可使活性增加至接近GTP所观察到的活性。直接在心脏线粒体基质中测定的核苷二磷酸激酶的比活性约为添加GDP后诱导的ATP支持的琥珀酸硫激酶比活性的15%。通过甘油密度梯度离心获得了兔心脏线粒体基质中核苷二磷酸激酶与琥珀酸硫激酶之间形成复合物的证据。有人提出，核苷二磷酸激酶与琥珀酸硫激酶的结合激活了前者的酶，解释了所观察到的ATP支持的琥珀酰辅酶A合成酶活性，并参与了将三羧酸循环中产生的GTP的高能磷酸转移至ATP池的过程。
