A method for producing mechanical paper pulp comprises: impregnating unprocessed wood, whereby unprocessed wood is exposed to an impregnating composition comprising at least a laccase enzyme and a formula mediator (I), wherein R1 and R2 are identical or different groups, chosen from among a hydrogen atom, a hydrocarbon chain, linear or branched, saturated or unsaturated, comprising 1 to 14 carbon atoms, wherein each hydrocarbon chain can be replaced by one or more functional groups chosen from among —OH, —SO3, benzyl, amino, mercapto, keto or carboxyl, wherein R1 and R2 in combination can form a cyclical structure, to achieve impregnation of the wood; and mechanically refining the impregnated wood, such that a mechanical paper pulp is obtained. The disclosure also relates to an impregnating composition used in this method and to the use thereof in a method for producing mechanical paper pulp, as well as to a method for producing paper.