초록
<P>Although overexpression of the <I>tHMG1</I> gene is a well-known strategy for terpene synthesis in <I>Saccharomyces cerevisiae</I>, the optimal level for tHMG1p has not been established. In the present study, it was observed that two copies of the <I>tHMG1</I> gene on a dual gene expression cassette improved squalene synthesis in laboratory strain by 16.8-fold in comparison to single-copy expression. It was also observed that tHMG1p is limited by its cofactor (NADPH), as the overexpression of NADPH regenerating genes’, viz., <I>ZWF1</I> and <I>POS5</I> (full length and without mitochondrial presequence), has led to its increased enzyme activity. Further, it was demonstrated that overexpression of full-length <I>POS5</I> has improved squalene synthesis in cytosol. Finally, when <I>tHMG1</I> and full-length <I>POS5</I> were co-overexpressed there was a net 27.5-fold increase in squalene when compared to control strain. These results suggest novel strategies to increase squalene accumulation in <I>S. cerevisiae</I>.</P><P><B>Graphic Abstract</B><BR><IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jafcau/2017/jafcau.2017.65.issue-37/acs.jafc.7b02945/production/images/medium/jf-2017-02945g_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jf7b02945'>ACS Electronic Supporting Info</A></P>