New insights on unspecific peroxygenases: superfamily reclassification and evolution.

BACKGROUND: Unspecific peroxygenases (UPO) (EC 1.11.2.1) represent an intriguing oxidoreductase sub-subclass of heme proteins with peroxygenase and peroxidase activity. With over 300 identified substrates, UPOs catalyze numerous oxidations including 1- or 2- electron oxygenation, selective oxyfunctionalizations, which make them most significant in organic syntheses and potentially attractive as industrial biocatalysts. There are very few UPOs available with distinct properties, notably, MroUPO which shows behavior ranging between UPO and another heme-thiolate peroxidase, called Chloroperoxidase (CPO). It prompted us to search for more UPOs in fungal kingdom which led us to studying their relationship with CPO.

RESULTS: In this study, we searched for novel UPOs in more than 800 fungal genomes and found 113 putative UPO-encoding sequences distributed in 35 different fungal species (or strains), amongst which single sequence per species were subjected to phylogeny study along with CPOs. Our phylogenetic study show that the UPOs are distributed in Basidiomycota and Ascomycota phyla of fungi. The sequence analysis helped to classify the UPOs into five distinct subfamilies: classic AaeUPO and four new subfamilies with potential new traits. We have also shown that each of these five subfamilies (supported by) have their own signature motifs. Surprisingly, some of the CPOs appeared to be a type of UPOs indicating that they were previously identified incorrectly. Selection pressure was observed on important motifs in UPOs which could have driven their functional divergence. Furthermore, the sites having different evolutionary rates caused by the functional divergence were also identified on some motifs along with the other relevant amino acid residues. Finally, we predicted critical amino acids responsible for the functional divergence in the UPOs and identified some sequence differences among UPOs, CPOs, and MroUPO to predict it's ranging behavior.

CONCLUSION: This study discovers new UPOs, provides a glimpse of their evolution from CPOs, and presents new insight on their functional divergence. We present a new classification of UPOs and shed new light on its phylogenetics. These different UPOs may exhibit a wide range of characteristics and specificities which may help in various fields of synthetic chemistry and industrial biocatalysts, and may as well lead to an advancement towards the understanding of physiological role of UPOs in fungi.