Fatty Acid Chain Shortening by a Fungal Peroxygenase.

A recently discovered peroxygenase from the fungus Marasmius rotula (MroUPO) 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 H2 O2 . The mechanism, analyzed using H218 O2 , starts with an α-oxidation catalyzed by MroUPO 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 MroUPO shortening carboxylic acid chains.

Biodegradation of lignocellulosics: microbial, chemical, and enzymatic aspects of the fungal attack of lignin / Biodegradación de la lignocelulosa: aspectos microbiológicos, químicos y enzimáticos del ataque fúngico a la lignina

Wood is the main renewable material on Earth and is largely used as building material and in paper-pulp manufacturing. This review describes the composition of lignocellulosic materials, the different processes by which fungi are able to alter wood, including decay patterns caused by white, brown, and soft-rot fungi, and fungal staining of wood. The chemical, enzymatic, and molecular aspects of the fungal attack of lignin, which represents the key step in wood decay, are also discussed. Modern analytical techniques to investigate fungal degradation and modification of the lignin polymer are reviewed, as are the different oxidative enzymes (oxidoreductases) involved in lignin degradation. These include laccases, high redox potential ligninolytic peroxidases (lignin peroxidase, manganese peroxidase, and versatile peroxidase), and oxidases. Special emphasis is given to the reactions catalyzed, their synergistic action on lignin, and the structural bases for their unique catalytic properties. Broadening our knowledge of lignocellulose biodegradation processes should contribute to better control of wood-decaying fungi, as well as to the development of new biocatalysts of industrial interest based on these organisms and their enzymes (AU)

La madera es el principal material renovable en la Tierra y es utilizada en gran parte como material de construcción y en la fabricación de celulosa. Esta revisión describe la composición de los materiales lignocelulósicos y diversos procesos de alteración de la madera por parte de hongos, como el deterioro causado por los llamados hongos de podredumbre blanca, de podredumbre parda y de podredumbre blanda y por los hongos cromógenos o manchadores de la madera. También se tratan los aspectos químicos, enzimáticos y moleculares del ataque a la lignina por los hongos, que es clave en el deterioro de la madera. Se describen las técnicas analíticas modernas para investigar la degradación y la modificación del polímero de la lignina causadas por hongos, así como las diversas enzimas oxidativas (oxidoreductasas) que intervienen en la degradación de la lignina. Entre éstas se encuentran lacasas, peroxidasas ligninolíticas de alto potencial redox (lignina-peroxidasa, manganeso-peroxidasa y peroxidasas versátiles) y las oxidasas. Se destacan las reacciones catalizadas, su acción sinérgica sobre la lignina, y las bases estructurales de sus exclusivas propiedades catalíticas. Un mejor conocimiento de los procesos de biodegradación de la lignocelulosa debería contribuir a un mejor control de los hongos descomponedores de la madera, así como al desarrollo de nuevos biocatalizadores de interés industrial basados en estos organismos y sus enzimas (AU)