Chloroperoxidase (CPO) is a versatile heme peroxidase isolated from the marine fungus Caldariomyces fumago. CPO has an active heme center coordinated to a proximal cysteine residue. The strong electron donating property of CPO’s proximal ligand has been suggested to provide the “push effect” during the cleavage of the peroxide bond to afford the formation of the reactive species, Compound I. The electron donating properties of the thiolate is regulated by the proximal ligand loop via hydrogen bond(s) between adjacent residues and the proximal thiolate. Mutagenesis approaches were used to evaluate the importance of residues adjacent to the proximal cysteine in CPO catalysis. The proline residues that sandwich the proximal cysteine were mutated to alanine and the resulting CPO mutants are characterized using various spectroscopic and biochemical methods. Our results suggested that the mutants displayed quite different spectroscopic characteristics from the wild-type CPO. This study demonstrated that redox potential might play a subtle role in halogenation reactions than what previous studies have implicated.

Elucidating the role of the proximal ligand loop in chloroperoxidase catalysis

254th National Meeting (2017)

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