Abstract
Cysteine dioxygenase (CDO) catalyzes the oxidation of cysteine to cysteine sulfinate, which has crucial roles in the metabolism and bioconversion. The catalyzed reaction mechanism of CDO is currently disputed. Herein, a high-spin " Fe -proximal oxygen" catalytic mechanism of rat CDO is theoretically investigated with an energy barrier of 15.7 kcal⋅mol-1. In the mechanism, the Fe -proximal oxygen atom firstly attacks the sulfur atom of cysteine by the swing of O (1)– O (2) bond, and this makes the Fe -proximal oxygen atom O (1) accessible to S and Fe -terminal oxygen atom O (2) be closed to Fe . Then the generated seven-membered ring intermediate has smaller tension and could help the reaction take place easily. The reaction ends in the formation of the product cysteine sulfinic acid with the second oxygen atom O (2) transferred to S. This study gives an additional insight of the reaction mechanism of CDO, where the " Fe -proximal oxygen" and " Fe -terminal oxygen" mechanisms are both favorable in the catalytic process.
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