ABSTRACTHaloarcula japonica, an extremely halophilic archaeon that requires high concentrations of NaCl for growth, accumulates the C50carotenoid bacterioruberin (BR). By homology analysis, a gene cluster, includingc0507,c0506, andc0505, was found and predicted to be involved in the synthesis of bacterioruberin. To elucidate the function of the encoded enzymes, we constructedHa. japonicamutants of these genes and analyzed carotenoids produced by the mutants. Our research showed thatc0507,c0506, andc0505encoded a carotenoid 3,4-desaturase (CrtD), a bifunctional lycopene elongase and 1,2-hydratase (LyeJ), and a C50carotenoid 2″,3″-hydratase (CruF), respectively. The above three carotenoid biosynthetic enzymes catalyze the reactions that convert lycopene to bacterioruberin inHa. japonica. This is the first identification of functional CrtD and CruF in archaea and elucidation of the complete biosynthetic pathway of bacterioruberin from lycopene.
IMPORTANCEHaloarcula japonica, an extremely halophilic archaeon, accumulates the C50carotenoid bacterioruberin (BR). In this study, we have identified three BR biosynthetic enzymes and have elucidated their functions. Among them, two enzymes were found in an archaeon for the first time. Our results revealed the biosynthetic pathway responsible for production of BR inHa. japonicaand provide a basis for investigating carotenoid biosynthetic pathways in other extremely halophilic archaea. Elucidation of the carotenoid biosynthetic pathway inHa. japonicamay also prove useful for producing the C50carotenoid BR efficiently by employing genetically modified haloarchaeal strains.
摘要THaloarcula japonica 是一种极其嗜卤的古生菌,需要高浓度的 NaCl 才能生长,它积累了 C50 类胡萝卜素细菌素(BR)。通过同源性分析,发现了一个基因簇,包括c0507、c0506和c0505,并推测它们参与了细菌绿蛋白的合成。为了阐明编码酶的功能,我们构建了这些基因的日本姬蛙突变体,并对突变体产生的类胡萝卜素进行了分析。研究表明,c0507、c0506和c0505分别编码类胡萝卜素3,4-去饱和酶(CrtD)、双功能番茄红素伸长酶和1,2-水合酶(LyeJ)以及C50类胡萝卜素2″,3″-水合酶(CruF)。上述三种类胡萝卜素生物合成酶催化了番茄红素转化为细菌素的反应。这是首次在古细菌中鉴定出功能性的 CrtD 和 CruF,并阐明了番茄红素转化为细菌素的完整生物合成途径。重要意义嗜卤古细菌(Haloarcula japonica)积累了 C50 类胡萝卜素细菌素(BR)。在这项研究中,我们发现了三种BR生物合成酶,并阐明了它们的功能。其中,有两种酶是首次在古生物中发现的。我们的研究结果揭示了嗜卤古细菌产生类胡萝卜素的生物合成途径,为研究其他嗜卤古细菌类胡萝卜素的生物合成途径提供了基础。对日本嗜卤古细菌类胡萝卜素生物合成途径的阐明也可能有助于利用转基因卤代古细菌菌株高效生产 C50 类胡萝卜素 BR。