Activation of Chloroperoxidase (CPO) to Cpd I through conversion from Cpd 0 is rate determined by simultaneous proton transfer of glutamic acid and concomitant heterolytic O-O cleavage.  Our focus is on elucidating the contribution of the proximal ligand, cysteine, to the energy of reaction and reaction barrier.  It has been proposed that the anionic nature of the thiolate raises the pKa of Compound 0, resulting in proton induced heterolytic cleavage of O-O.  It has also been suggested that proximal ligand protonation favors O-O bond scission.  To distinguish these claims, we present a comparative analysis of the thiolate, thiol, and hydrogen bonded thiolate and thiol via DFT calculations, where DE and reaction barriers are examined.  It has been shown that neutral cysteine is a viable proximal ligand for CPO and related enzymes, but the reactivity of this form of the enzyme has not been previously assessed.

Comparitive quantum chemical study of thiolate, thiol, and hydrogen bonded thiol and thiolate proximal heme ligands on the rate determining step of CPO activation to Compound I

243rd National Meeting (2012)

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