CATALYTIC TRANSFER OF HYDRIDE IONS FROM NADPH TO OXYGEN BY THE INTERCONVERSIONS OF PROLINE AND DELTA-1-PYRROLINE-5-CARBOXYLATE
CATALYTIC TRANSFER OF HYDRIDE IONS FROM NADPH TO OXYGEN BY THE INTERCONVERSIONS OF PROLINE AND DELTA-1-PYRROLINE-5-CARBOXYLATE
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DOI：
10.1016/0003-9861(86)90413-3
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发表时间：
1986-07-01
影响因子：
3.9
通讯作者：
PHANG, JM
中科院分区：
文献类型：
--
作者：
HAGEDORN, CH;PHANG, JM
在重构系统中的研究表明，脯氨酸和Δ 1-吡咯啉-5-羧酸的相互转化可以构成穿梭，其将还原当量作为脯氨酸转移到线粒体中，并将氧化电位作为Δ 1-吡咯啉-5-羧酸转移出去。本文报道的研究确定了还原当量的转移是否可以在化学计量上大于穿梭中间体的利用。首先，在含有线粒体颗粒和吡咯啉-5-羧酸还原酶的系统中，在Δ 1-吡咯啉-5-羧酸可再循环回脯氨酸的条件下，使用由[5- 3 H]脯氨酸产生的3 HOH来定量脯氨酸氧化。在平行孵育中，测定了[U-14 C]脯氨酸的代谢结局。3 HOH产量继续增加，而14 C-标记的脯氨酸和Δ 1-吡咯啉-5-羧酸酯没有发生净变化，表明该系统中的催化活性。在另一个含有完整线粒体和吡咯啉-5-羧酸还原酶的系统中，通过[U-14 C]脯氨酸回收率和[5- 3 H]脯氨酸的3 HOH产生来定量脯氨酸氧化。在缺乏NADPH和吡咯啉-5-羧酸还原酶的孵育中，两种方法的脯氨酸氧化相同。然而，它是显着低估了[U-14 C]脯氨酸的回收率相比，在含有所有穿梭组件的孵育中的3 HOH生产。这些结果表明所提出的穿梭在含有完整线粒体的重构系统中的催化功能。这种穿梭可以在特定的时间发挥作用，催化产生胞质NADP+，并反过来调节受[NADP+]限制的酶。我们认为，拟议的穿梭可能起到增加核糖-5-磷酸合成的戊糖磷酸途径的氧化分支，反过来增加PP-核糖-P和嘌呤的合成在细胞生长的启动。
Studies in reconstituted systems indicate that the interconversions of proline and .DELTA.1-pyrroline-5-carboxylate can constitute a shuttle which transfers reducing equivalents into mitochondria as proline and oxidizing potential out as .DELTA.1-pyrroline-5-carboxylate. The studies reported here determine if the transfer of reducing equivalents can be stoichiometrically greater than the utilization of shuttle intermediates. First, 3HOH production from [5-3H]proline was used to quantitate proline oxidation under conditions where .DELTA.1-pyrroline-5-carboxylate could recycle back to proline in a system containing mitochondrial particles and pyrroline-5-carboxylate reductase. In parallel incubations the metabolic fate of [U-14C]proline was determined. 3HOH production continued to increase while no net change occurred in 14C-labeled proline and .DELTA.1-pyrroline-5-carboxylate indicating catalytic activity in this system. In another system that contained intact mitochondria and pyrroline-5-carboxylate reductase, proline oxidation was quantitate by both [U-14C]proline recoveries and 3HOH production from [5-3H]proline. Proline oxidation was the same by both methods in incubations lacking NADPH and pyrroline-5-carboxylate reductase. However, it was significantly underestimated by [U-14C]proline recoveries as compared to 3HOH production in incubations containing all shuttle components. These results indicate catalytic functioning of the proposed shuttle in a reconstituted system containing intact mitochondria. This shuttle may function at specific times to catalytically generate cytosolic NADP+ and in turn regulate enzymes limited by [NADP+]. We suggest that the proposed shuttle may function to increase ribose-5-phosphate synthesis by the oxidative limb of the pentose phosphate pathway and inturn increase PP-ribose-P and purine synthesis during the initiation of cell growth.