Functional coupling between enzymes of the chromaffin granule membrane.
Functional coupling between enzymes of the chromaffin granule membrane.
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嗜铬颗粒膜酶之间的功能耦合。
DOI：
10.1016/s0021-9258(18)67577-5
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发表时间：
1986
期刊：
影响因子：
--
通讯作者：
G. Radda
中科院分区：
文献类型：
--
作者：
L. Wakefield;A. E. Cass;G. Radda
利用光学差光谱法研究了细胞色素b561与肾上腺嗜铬颗粒的其他氧化还原活性成分的反应。结果表明，细胞色素和多巴胺β-羟化酶之间没有直接的电子转移，但在抗坏血酸存在下，多巴胺β-羟化酶的周转导致细胞色素的氧化，这部分被线粒体NADH：A-的作用逆转。氧化还原酶。因此，这三种蛋白质可以通过抗坏血酸在功能上偶联。通过EPR测量的细胞色素的氧化还原状态和抗坏血酸自由基浓度之间的关系的定量研究表明，抗坏血酸减少细胞色素在一个电子转移反应。跨颗粒膜的质子电化学梯度的产生仅引起细胞色素中点电位的小的（20 mV）增加，表明细胞色素不是质子泵。这些数据是一致的模型，其中细胞色素b561，通过与抗坏血酸或抗坏血酸自由基的颗粒膜的任何一侧反应，可以耦合抗坏血酸消耗反应的多巴胺β-羟化酶内的嗜铬颗粒的抗坏血酸再生反应的NADH：A-。线粒体外膜上的氧化还原酶。颗粒膜上的H+-ATP酶既能驱动电子从胞液流向颗粒，又能补充颗粒内多巴胺β-羟化酶周转所消耗的质子。
The reactions of cytochrome b561 with other redox-active components of the adrenal chromaffin granule were examined using optical difference spectroscopy. It was shown that there is no direct electron transfer between the cytochrome and dopamine beta-hydroxylase, but that in the presence of ascorbate, turnover of dopamine beta-hydroxylase causes an oxidation of the cytochrome, which is partially reversed by the action of the mitochondrial NADH:A-. oxidoreductase. Thus, these three proteins may be functionally coupled via ascorbate. A quantitative study of the relationship between the redox state of the cytochrome and the ascorbate radical concentration measured by EPR showed that ascorbate reduces the cytochrome in a one-electron transfer reaction. Generation of a proton electrochemical gradient across the granule membrane causes only a small (20 mV) increase in the cytochrome midpoint potential suggesting the cytochrome is not a proton pump. The data are consistent with a model in which cytochrome b561, by reacting with ascorbate or ascorbate free radical on either side of the granule membrane, could couple the ascorbate-consuming reaction of the dopamine beta-hydroxylase inside the chromaffin granule to the ascorbate-regenerating reaction of the NADH:A-. oxidoreductase on the outer mitochondrial membrane. The H+-ATPase of the granule membrane could both drive the flow of electrons in the direction from cytosol to granule and replenish protons consumed by the turnover of dopamine beta-hydroxylase inside the granule.