The mechanism of succinate or fumarate transfer in the tricarboxylic acid cycle allows molecular rotation of the intermediate.
The mechanism of succinate or fumarate transfer in the tricarboxylic acid cycle allows molecular rotation of the intermediate.
复制标题
三羧酸循环中琥珀酸或富马酸转移的机制允许中间体的分子旋转。
DOI：
10.1016/0003-9861(90)90026-u
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发表时间：
1990
影响因子：
3.9
通讯作者：
Tompa,P
中科院分区：
文献类型：
--
作者：
Bernhard,SA;Tompa,P
将线粒体与l [5- 13 C]谷氨酸一起孵育，并通过13 C NMR确定所形成的l-天冬氨酸的两个羧基碳原子之间的标记物分布。从L-谷氨酸到天冬氨酸的反应顺序跨越了涉及两个对称中间体琥珀酸酯和富马酸酯的三羧酸循环反应。原则上，这些中间体的C2对称性允许区分它们在其生产和利用的酶位点之间的转移机制。仅通过翻译将代谢物从一个位点直接转移到另一个位点，预测了天冬氨酸C1和C4之间13 C的不均匀分布，而转移过程中的分子旋转允许原始C5标记的混乱。在不同的谷氨酸浓度和溶剂渗透压的几种条件下，观察到天冬氨酸的C1和C4碳中的相等标记。这一观察结果与限制两种中间体分子旋转的转移机制不一致，但与随机扩散和直接转移机制兼容，前提是后者允许分子旋转。
Mitochondria were incubated withl[5-13C]glutamic acid and the distribution of the label between the two carboxyl carbon atoms of thel-aspartic acid formed was determined by13C NMR. The reaction sequence leading froml-glutamic acid tol-aspartic acid spans the tricarboxylic acid cycle reactions involving the two symmetrical intermediates succinate and fumarate. The C2 symmetry of these intermediates in principle permits a discrimination of the mechanism of their transfer between their enzyme sites of production and utilization. A direct transfer of metabolite from site to site by translation alone predicts an unequal distribution of13C between the C1 and C4 of aspartate, whereas molecular rotation during transfer allows for a scrambling of the original C5 label. Under several conditions of different glutamate concentrations and solvent osmotic pressures, equal labeling in the C1 and C4 carbons of aspartate is observed. This observation is inconsistent with a transfer mechanism restricting molecular rotation for both intermediates but is compatible with both a random diffusion and a direct transfer mechanism provided the latter allows molecular rotation.