For carotenogenesis, two biosynthetic pathways from phytoene to lycopene are known. Most bacteria and fungi require only phytoene desaturase (PDS, CrtI), whereas land plants require four enzymes: PDS (CrtP), ζ-carotene desaturase (ZDS, CrtQ), ζ-carotene isomerase (Z-ISO) and cis-carotene isomerase (CrtISO, CrtH). The gene encoding Z-ISO has been functionally identified in only two species, Arabidopsis thaliana and Zea mays, and has been little studied in other organisms. In this study, we found that the deduced amino acid sequences of Arthrospira Z-ISO and Euglena Z-ISO have 58% and 62% identity, respectively, with functional Z-ISO from Arabidopsis. We studied the function of Z-ISO genes from the cyanobacterium Arthrospira platensis and eukaryotic microalga Euglena gracilis. The Z-ISO genes of Arthrospira and Euglena were transformed into Escherichia coli strains that produced mainly 9,15,9'-tri-cis-ζ-carotene in darkness. In the resulting E. coli transformants cultured under darkness, 9,9'-di-cis-ζ-carotene was accumulated predominantly as Z-ISO in Arabidopsis. This indicates that the Z-ISO genes were involved in the isomerization of 9,15,9'-tri-cis-ζ-carotene to 9,9'-di-cis-ζ-carotene in darkness. This is the first functional analysis of Z-ISO as a ζ-carotene isomerase in cyanobacteria and eukaryotic microalgae. Green sulfur bacteria and Chloracidobacterium also use CrtP, CrtQ and CrtH for lycopene synthesis as cyanobacteria, but their genomes did not comprise Z-ISO genes. Consequently, Z-ISO is needed in oxygenic phototrophs, whereas it is not found in anoxygenic species.

中文翻译：

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产氧营养养分素需要ζ-胡萝卜素异构酶（Z-ISO）进行胡萝卜素合成：节肢动物和裸藻的功能分析。

对于胡萝卜素生成，已知有从八氢番茄红素到番茄红素的两种生物合成途径。大多数细菌和真菌仅需要八氢番茄红素去饱和酶（PDS，CrtI），而陆地植物则需要四种酶：PDS（CrtP），ζ-胡萝卜素去饱和酶（ZDS，CrtQ），ζ-胡萝卜素异构酶（Z-ISO）和顺式胡萝卜素异构酶（CrtISO，CrtH）。仅在两个物种（拟南芥和玉米）中功能上鉴定了编码Z-ISO的基因，而在其他生物中很少进行研究。在这项研究中，我们发现，拟南芥Z-ISO和Euglena Z-ISO的推导氨基酸序列与拟南芥的功能性Z-ISO分别具有58％和62％的同一性。我们研究了来自蓝藻关节杆菌和真核微藻Euglena gracilis的Z-ISO基因的功能。Arthrospira和Euglena的Z-ISO基因被转化到大肠杆菌菌株中，该菌株在黑暗中主要产生9,15,9'-tri-cis-ζ-胡萝卜素。在黑暗中培养的所得大肠杆菌转化子中，9,9'-二-顺-ζ-胡萝卜素主要作为拟南芥中的Z-ISO积累。这表明Z-ISO基因参与了在黑暗中将9,15,9'-三顺式-ζ-胡萝卜素异构化为9,9'-di-顺式-ζ-胡萝卜素。这是Z-ISO在蓝细菌和真核微藻中作为ζ-胡萝卜素异构酶的第一个功能分析。绿硫细菌和绿杆菌也将CrtP，CrtQ和CrtH用于番红花素的合成作为蓝细菌，但它们的基因组不包含Z-ISO基因。因此，在氧光养生物中需要Z-ISO，而在产氧物种中则找不到Z-ISO。