MOLECULAR-OXYGEN AND THE STATE OF GEOMETRIC ISOMERISM OF INTERMEDIATES ARE ESSENTIAL IN THE CAROTENE DESATURATION AND CYCLIZATION REACTIONS IN DAFFODIL CHROMOPLASTS
MOLECULAR-OXYGEN AND THE STATE OF GEOMETRIC ISOMERISM OF INTERMEDIATES ARE ESSENTIAL IN THE CAROTENE DESATURATION AND CYCLIZATION REACTIONS IN DAFFODIL CHROMOPLASTS
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DOI：
10.1111/j.1432-1033.1989.tb15000.x
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发表时间：
1989-09-01
期刊：
影响因子：
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通讯作者：
KLEINIG, H
中科院分区：
文献类型：
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作者：
BEYER, P;MAYER, M;KLEINIG, H
在体外，通过改变孵育参数O2和LIGH，水仙有色质体膜结合的胡萝卜素合成反应序列可以细分为三个反应片段。在第一段中，15-顺式植烯在黑暗中和氧气作为基本辅因子存在的情况下脱饱和为15-顺式-zeta-胡萝卜素(反式消除氢)。积累的zeta-胡萝卜素的15-顺式双键的光异构化是第二段功能的先决条件，即去饱和为7，9，9‘，7’-四顺-番茄红素(原番茄红素，顺式消除氢气)。讨论了O2作为电子受体的作用，并提出了氧化还原酶在去饱和酶(形成多烯生色团)和O2之间起氧化还原中介作用的证据。提出了一种类似于硬脂酰基载体蛋白去饱和的现象，这种现象也存在于叶绿体中。第三部分，原番茄红素的环化反应，只有在没有氧气的情况下才活跃，并涉及额外的顺反异构化反应。
The membrane-bound carotensogenic reaction sequence in daffodil chromoplasts can be subdivided in vitro into three reaction segments by varying the incubation parameters O2 and light. In the first segment, 15-cis-phytoene is desaturated to 15-cis-.zeta.-carotene (trans elimination of hydrogen) in the dark and in the presence of O2 as an essential cofactor. A photoisomerization of the 15-cis double bond of the accumulated .zeta.-carotene to trans is the prerequisite for the function of the second segment, the desaturation to 7,9,9'',7''-tetra-cis-lycopene (prolycopene, cis elimination of hydrogen). The role of O2 as an electron acceptor is discussed and evidence for an oxidorectase acting as a redox mediator between the desaturase (forming the polyene chromophore) and O2 is presented. A certain analogy to the desaturation of stearoyl-carrier protein, which also occurs in plastids, is proposed. The third segment, the cyclization of prolycopene, is active only in the absence of O2 and involves additional cis-trans isomerization reactions.