Insect multicopper oxidases: Diversity, properties, and physiological roles

Multicopper oxidases (MCOs) are a group of related proteins that are ubiquitous in nature. They perform a wide variety of functions including pigmentation, lignin synthesis and degradation, iron homeostasis, and morphogenesis. The laccases of fungi are intensely studied for their biotechnological potential as a more environmentally friendly alternative to harsh or toxic chemicals used for certain industrial applications. Research into insect MCOs has recently attracted renewed interest as it is evident that they have diverse roles in insect physiology. MCO mRNA or enzymatic activity has been detected in extracts from epidermis, midgut, Malpighian tubules, salivary glands, and reproductive tissues. Genome sequencing has allowed for the identification of MCO genes and revealed that the number of genes can vary between species. The function of one of the genes, MCO2, has been demonstrated to be a laccase-type phenoloxidase critical for cuticle sclerotization. However, the enzymatic properties and physiological functions of the remaining MCOs remain to be elucidated. A better understanding of the roles MCOs play in insect biology may help to develop new control measures of pest species.