응용화학과 > 교육과정 및 세미나 > 세미나 및 학술행사

* 초록 :

Pericyclic reactions such as sigmatropic rearrangements and some cycloaddition reactions have been extensively utilized in numerous synthetic applications due to their power to construct multiple C-C bonds with great selectivity. In contrast, usage of this type of reactions in “life” has been rarely witnessed, in that chorimate mutase catalyzing a Claisen rearrangement and its relatives are the only known examples so far. In the past two decades, a lot of research efforts have been invested, particularly, to find an enzyme to catalyze a Diels-Alder reaction, one of prototypical pericyclic reactions, and have led to identification of a number of putative Diels-Alderases. Nonetheless, robust experimental data to distinguish whether they indeed catalyze Diels-Alder reactions have yet to be presented and, hence, the existence of a Diels-Alderase is still obscure. In hope to answer this fundamental question, we conducted a thorough investigation on the biosynthesis of a polyketide natural product, spinosyn A, since construction of its tetracyclic framework had been proposed to involve an intramolecular Diels-Alder reaction. In this study, we were able to fully elucidate its biosynthetic sequence as well as functions of enzymes involved therein. Importantly, through careful kinetic analysis, we could unequivocally reveal that one of these enzymes, SpnF, is capable of specifically catalyzing a [4+2] cycloaddition reaction. The characterized function and catalysis of SpnF are unique and unprecedented. Therefore, in-depth analysis of its catalytic origin is anticipated to set a stage for bringing new perspective and opportunities to examine pericyclic reactions in life.

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