Department of Biotechnology, SINTEF Materials and Chemistry, Sem Sælands vei 2a, NO-7465 Trondheim, Norway.
J Bacteriol. 2010 Nov;192(21):5688-99. doi: 10.1128/JB.00724-10. Epub 2010 Aug 27.
We report the cloning and characterization of the biosynthetic gene cluster (crtE, crtB, crtI, crtE2, crtYg, crtYh, and crtX) of the γ-cyclic C(50) carotenoid sarcinaxanthin in Micrococcus luteus NCTC2665. Expression of the complete and partial gene cluster in Escherichia coli hosts revealed that sarcinaxanthin biosynthesis from the precursor molecule farnesyl pyrophosphate (FPP) proceeds via C(40) lycopene, C(45) nonaflavuxanthin, C(50) flavuxanthin, and C(50) sarcinaxanthin. Glucosylation of sarcinaxanthin was accomplished by the crtX gene product. This is the first report describing the biosynthetic pathway of a γ-cyclic C(50) carotenoid. Expression of the corresponding genes from the marine M. luteus isolate Otnes7 in a lycopene-producing E. coli host resulted in the production of up to 2.5 mg/g cell dry weight sarcinaxanthin in shake flasks. In an attempt to experimentally understand the specific difference between the biosynthetic pathways of sarcinaxanthin and the structurally related ε-cyclic decaprenoxanthin, we constructed a hybrid gene cluster with the γ-cyclic C(50) carotenoid cyclase genes crtYg and crtYh from M. luteus replaced with the analogous ε-cyclic C(50) carotenoid cyclase genes crtYe and crtYf from the natural decaprenoxanthin producer Corynebacterium glutamicum. Surprisingly, expression of this hybrid gene cluster in an E. coli host resulted in accumulation of not only decaprenoxanthin, but also sarcinaxanthin and the asymmetric ε- and γ-cyclic C(50) carotenoid sarprenoxanthin, described for the first time in this work. Together, these data contributed to new insight into the diverse and multiple functions of bacterial C(50) carotenoid cyclases as key catalysts for the synthesis of structurally different carotenoids.
我们报道了微球菌 NCTC2665 中 γ-环 C(50)类胡萝卜素沙角黄素的生物合成基因簇(crtE、crtB、crtI、crtE2、crtYg、crtYh 和 crtX)的克隆和特征。在大肠杆菌宿主中表达完整和部分基因簇表明,沙角黄素的生物合成从前体分子法呢基焦磷酸(FPP)经过 C(40)番茄红素、C(45)非黄质、C(50)叶黄素和 C(50)沙角黄素进行。沙角黄素的糖基化由 crtX 基因产物完成。这是首次描述 γ-环 C(50)类胡萝卜素的生物合成途径。海洋微球菌 Otnes7 的相应基因在产番茄红素的大肠杆菌宿主中表达,导致在摇瓶中产生高达 2.5mg/g 细胞干重的沙角黄素。为了试图从实验上理解沙角黄素和结构相关的 ε-环脱甲羟戊烯基叶黄素生物合成途径之间的特定差异,我们构建了一个杂种基因簇,其中来自微球菌的 γ-环 C(50)类胡萝卜素环化酶基因 crtYg 和 crtYh 被来自天然脱甲羟戊烯基叶黄素产生菌谷氨酸棒杆菌的类似的 ε-环 C(50)类胡萝卜素环化酶基因 crtYe 和 crtYf 取代。令人惊讶的是,该杂种基因簇在大肠杆菌宿主中的表达不仅导致脱甲羟戊烯基叶黄素的积累,而且还导致沙角黄素和不对称的 ε-和 γ-环 C(50)类胡萝卜素 sarprenoxanthin 的积累,sarprenoxanthin 是在本工作中首次描述的。这些数据共同为细菌 C(50)类胡萝卜素环化酶作为合成结构不同类胡萝卜素的关键催化剂的多样化和多种功能提供了新的见解。