Substrate specificity of a novel squalene-hopene cyclase from Zymomonas mobilis

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• 作者：Miriam Seitz ; Janosch Klebensberger ; Sascha Siebenhaller ; Michael Breuer ; Gabriele Siedenburg ; Dieter Jendrossek ; Bernhard Hauer
• 关键词：Squalene-hopene cyclase ; Zymomonas mobilis ; Homofarnesol ; Citronellal ; Biocatalysis
• 刊名：Journal of Molecular Catalysis B: Enzymatic
• 出版年：2012
• 出版时间：December, 2012
• 年：2012
• 卷：84
• 期：Complete
• 页码：72-77
• 全文大小：511 K

文摘

Squalene-hopene cyclases (SHC; EC 5.4.99.17) catalyze the cyclization of triterpenoids via cationic intermediates in one of the most complex reactions known in biochemistry. In this study, we report the functional expression of a novel SHC from the ethanol producing bacterium Zymomonas mobilis (ZmoSHC1; YP_163283.1). Biochemical characterization of ZmoSHC1 uncovered unique substrate activity patterns compared to the previously reported AacSHC from Alicyclobacillus acidocaldarius and ZmoSHC2, the second squalene-hopene cyclase from Z. mobilis. ZmoSHC1 showed cyclization of the non-natural substrates homofarnesol (C₁₆) and citronellal (C₁₀) in addition to hopene formation from squalene (C₃₀). Moreover, ZmoSHC1 turned out to reveal high biocatalytic stability during long-term incubations. Remarkably, ZmoSHC1 exhibited a shift of activity towards substrates of shorter chain lengths, displaying over 50-fold higher conversion of homofarnesol and more than 2-fold higher conversion of citronellal in comparison to squalene conversion.