Structural Features and Reaction Profile of an Evolved Unspecific Peroxygenase From Candolleomyces Aberdarensis

Fungal unspecific peroxygenases (UPOs) are versatile biocatalysts capable of inserting oxygen into nonactivated C.H bonds. Despite their significance in organic synthesis, only a few UPOs have been characterized structurally and biochemically. In the current study, we provide insights into the structure and reaction profile of an unusual, acidic, long UPO from Candolleomyces aberdarensis that was evolved for heterologous expression in yeast. The crystal structure of the enzyme was resolved at a resolution of 1.8 Å, which helped to reveal several catalytic determinants that differ from those of canonical long UPOs. Cocrystallization experiments with alkanes, fatty acids, and the norisoprenoids α-damascone and α-ionone, were carried out together with the analysis of enzymatic reactions. With alkanes and fatty acids, the biocatalyst performs oxygenations at the ω−1 and ω−2 positions, producing diols and ketones. Conversely, the enzyme acts on the α-ionone ring and the vinylic aliphatic chain of α-damascone, generating 3-hydroxy-α-ionone and 10-hydroxy-α-damascone, respectively. The substrate preferences of this biocatalyst are marked by an intensely hydrophobic heme channel, with some residues protruding into the tunnel, and a characteristic catalytic tripod comprising a Met residue in a dual conformation. Molecular dynamics simulations revealed that enzyme catalysis is primarily driven by dynamic channel gating, ligand-specific preorganization within the access tunnel, and complex diffusion pathways leading to the active site.