Laccase: enzyme revisited and function redefined

One enzyme, one physiological role, that’s how most scientists have traditionally looked at it but there is a growing appreciation that some enzymes “moonlight” i.e. in addition to their “primary” catalytic function, they carry other functions as well. Moonlighting refers to a protein that has multiple functions, which are not because of gene fusion; splice variants or multiple proteolytic fragments. Until recently laccases were reported from eukaryotes, e.g. fungi, plants, insect. However there is some evidence for its existence in prokaryotes, a protein with typical features of multi-copper oxidase enzyme family. The present available knowledge of its structure provides a glimpse of its plasticity, revealing a multitude of binding sites responsible for multifunctional activity. Laccase represents an example of a ‘moonlighting’ protein that overcomes the one gene-one structure-one function concept to follow the changes of the organism in its physiological and pathological conditions. It is wide spread in plants, where it is involved in biosynthesis of lignin; in fungi it is involved in lignin degradation, development associated pigmentation (melanin synthesis), detoxification and pathogenesis, and in bacteria, laccases are involved in the synthesis of endospore coat protein (cot A).