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首页> 外文期刊>Journal of bacteriology >Elucidation of the Erwinia uredovora carotenoid biosynthetic pathway by functional analysis of gene products expressed in Escherichia coli.
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Elucidation of the Erwinia uredovora carotenoid biosynthetic pathway by functional analysis of gene products expressed in Escherichia coli.

机译：通过对大肠杆菌中表达的基因产物进行功能分析，阐明了维氏欧文氏菌类胡萝卜素的生物合成途径。

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The most important function of carotenoid pigments, especially beta-carotene in higher plants, is to protect organisms against photooxidative damage (G. Britton, in T. W. Goodwin, ed., Plant Pigments--1988, 1988; N. I. Krinsky, in O. Isler, H. Gutmann, and U. Solms, ed., Carotenoids--1971, 1971). beta-Carotene also functions as a precursor of vitamin A in mammals (G. A. J. Pitt, in I. Osler, H. Gutmann, and U. Solms, ed., Carotenoids--1971, 1971). The enzymes and genes which mediate the biosynthesis of cyclic carotenoids such as beta-carotene are virtually unknown. We have elucidated for the first time the pathway for biosynthesis of these carotenoids at the level of enzyme-catalyzed reactions, using bacterial carotenoid biosynthesis genes. These genes were cloned from a phytopathogenic bacterium, Erwinia uredovora 20D3 (ATCC 19321), in Escherichia coli and located on a 6,918-bp fragment whose nucleotide sequence was determined. Six open reading frames were found and designated the crtE, crtX, crtY, crtI, crtB, and crtZ genes in reference to the carotenoid biosynthesis genes of a photosynthetic bacterium, Rhodobacter capsulatus; only crtZ had the opposite orientation from the others. The carotenoid biosynthetic pathway in Erwinia uredovora was clarified by analyzing carotenoids accumulated in E. coli transformants in which some of these six genes were expressed, as follows: geranylgeranyl PPiCrtB----prephytoene PPiCrtE----phytoeneCrtI---- lycopeneCrtY----beta-caroteneCrtZ----zeaxanthinCrtX--- -zeaxanthin-beta- diglucoside. The carotenoids in this pathway appear to be close to those in higher plants rather than to those in bacteria. Also significant is that only one gene product (CrtI) for the conversion of phytoene to lycopene is required, a conversion in which four sequential desaturations should occur via the intermediates phytofluene, zeta-carotene, and neurosporene.
机译：类胡萝卜素颜料，尤其是高等植物中的β-胡萝卜素，最重要的功能是保护生物体免受光氧化损害（G. Britton，在TW Goodwin编辑，《植物颜料》，1988，1988; NI Krinsky，在O. Isler。 ，H.Gutmann和U.Solms编辑，类胡萝卜素-1971年，1971年）。 β-胡萝卜素在哺乳动物中也可作为维生素A的前体（G.A. J. Pitt，I. Osler，H.Gutmann和U.Solms编辑，类胡萝卜素--1971，1971）。介导诸如β-胡萝卜素之类的环状类胡萝卜素的生物合成的酶和基因实际上是未知的。我们首次阐明了利用细菌类胡萝卜素生物合成基因在酶催化反应水平上生物合成这些类胡萝卜素的途径。这些基因是从植物病原性细菌欧文氏欧文氏菌20D3（ATCC 19321）中克隆到大肠杆菌中，并位于一个确定核苷酸序列的6,918-bp片段上。参照光合细菌荚膜红细菌的类胡萝卜素生物合成基因，找到了六个开放阅读框并命名为crtE，crtX，crtY，crtI，crtB和crtZ基因。只有crtZ的方向与其他方向相反。通过分析在大肠杆菌转化子中积累的类胡萝卜素来阐明雷氏欧文氏菌中的类胡萝卜素生物合成途径，其中表达了这六个基因中的一些，如下所示： ---β-胡萝卜素CrtZ ----玉米黄质CrtX ----玉米黄质-β-二葡糖苷。该途径中的类胡萝卜素似乎与高等植物中的类胡萝卜素相近，而不是细菌中的类胡萝卜素。同样重要的是，仅需要一个用于将八氢番茄红素转化为番茄红素的基因产物（CrtI），在这种转化中，应该通过四氢番茄红素，ζ-胡萝卜素和神经孢子中间体发生四个顺序的去饱和反应。

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