Perzl M, Reipen I G, Schmitz S, Poralla K, Sahm H, Sprenger G A, Kannenberg E L
Mikrobiologie/Biotechnologie, Universität Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany.
Biochim Biophys Acta. 1998 Jul 31;1393(1):108-18. doi: 10.1016/s0005-2760(98)00064-2.
The squalene-hopene cyclase (SHC) is the only enzyme involved in the biosynthesis of hopanoid lipids that has been characterized on the genetic level. To investigate if additional genes involved in hopanoid biosynthesis are clustered with the shc gene, we cloned and analyzed the nucleotide sequences located immediately upstream of the shc genes from Zymomonas mobilis and Bradyrhizobium japonicum. In Z. mobilis, five open reading frames (ORFs, designated as hpnA-E) were detected in a close arrangement with the shc gene. In B. japonicum, three similarly arranged ORFs (corresponding to hpnC-E from Z. mobilis) were found. The deduced amino acid sequences of hpnC-E showed significant similarity (58-62%) in both bacteria. Similarities to enzymes of other terpenoid biosynthesis pathways (carotenoid and steroid biosynthesis) suggest that these ORFs encode proteins involved in the biosynthesis of hopanoids and their intermediates. Expression of hpnC to hpnE from Z. mobilis as well as expression of hpnC from B. japonicum in Escherichia coli led to the formation of the hopanoid precursor squalene. This indicates that hpnC encodes a squalene synthase. The two additional ORFs (hpnA and hpnB) in Z. mobilis showed similarities to enzymes involved in the transfer and modification of sugars, indicating that they may code for enzymes involved in the biosynthesis of the complex, sugar-containing side chains of hopanoids.
鲨烯 - 藿烯环化酶（SHC）是参与类异戊二烯脂质生物合成的唯一一种在基因水平上已被表征的酶。为了研究参与类异戊二烯生物合成的其他基因是否与shc基因成簇，我们克隆并分析了来自运动发酵单胞菌和日本慢生根瘤菌的shc基因紧邻上游的核苷酸序列。在运动发酵单胞菌中，检测到五个开放阅读框（ORF，命名为hpnA - E）与shc基因紧密排列。在日本慢生根瘤菌中，发现了三个类似排列的ORF（对应于运动发酵单胞菌的hpnC - E）。在两种细菌中，hpnC - E推导的氨基酸序列显示出显著的相似性（58 - 62%）。与其他萜类生物合成途径（类胡萝卜素和类固醇生物合成）的酶的相似性表明，这些ORF编码参与类异戊二烯及其中间体生物合成的蛋白质。运动发酵单胞菌中hpnC至hpnE的表达以及日本慢生根瘤菌中hpnC在大肠杆菌中的表达导致了类异戊二烯前体鲨烯的形成。这表明hpnC编码鲨烯合酶。运动发酵单胞菌中的另外两个ORF（hpnA和hpnB）与参与糖转移和修饰的酶显示出相似性，表明它们可能编码参与类异戊二烯复杂含糖侧链生物合成的酶。
