Fatty Acid Chain Shortening by a Fungal Peroxygenase

A recently discovered peroxygenase from the fungus Marasmius rotula ( Mro UPO) is able to catalyze the progressive one‐carbon shortening of medium and long‐chain mono‐ and dicarboxylic acids by itself alone, in the presence of H 2 O 2 . The mechanism, analyzed using H 2 18 O 2 , starts with an α‐oxidation catalyzed by Mro UPO generating an α‐hydroxy acid, which is further oxidized by the enzyme to a reactive α‐keto intermediate whose decarboxylation yields the one‐carbon shorter fatty acid. Compared with the previously characterized peroxygenase of Agrocybe aegerita , a wider heme access channel, enabling fatty acid positioning with the carboxylic end near the heme cofactor (as seen in one of the crystal structures available) could be at the origin of the unique ability of Mro UPO shortening carboxylic acid chains.