Cloning, Expression And Functional Characterization Of Two Oxidosqualene Cyclases From Hoodia Gordonii

Oxidosqualene cyclases (OSCs) are the key enzymes responsible for cyclization of 2, 3-oxidosqualene to varied triterpenoids and phytosterols. Hoodia gordonii (Asclepiadacecae) a native of Kalahari deserts of South Africa, Namibia, and Botswana is one of the most prevalent herbal supplements for weight loss. The appetite suppressant properties are attributed to P57AS3, an oxypregnane steroidal glycoside. At the molecular level, the enzymes involved in biosynthesis of triterpenes and phytosterols from H. gordonii have not been reported in the literature. In the present investigation, predicted transcripts potentially encoding oxidosqualene cyclases, were first identified by mining publicly-available H. gordonii RNA-seq data sets. Recombinant enzyme studies with two of the OSCs-like sequences led to the identification of HgCS1 and HgCS2, encoding lupeol and cycloartenol synthases, respectively. GC-MS predicted the HgCS1 reaction product as lupeol, and the structure is confirmed using NMR.

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