Fungal extracellular enzyme activity

[1] Biopolymers are structurally complex and require the combined actions of a community of diverse microorganisms and their secreted exoenzymes to depolymerize the polysaccharides into easily assimilable monomers.

The cycling of elements from dead organic matter by heterotrophic soil microorganisms is essential for nutrient turnover and energy transfer in terrestrial ecosystems.

By hydrolyzing plant cell wall polymers, microbes release energy that has the potential to be used by humans as biofuel.

The varied chemical structure of organic matter requires a suite of extracellular enzymes to access the carbon and nutrients embedded in detritus.

[12] To detect the presence of complex polymers, some exoenzymes are produced constitutively at low levels, and expression is upregulated when the substrate is abundant.

[13] This sensitivity to the presence of varying concentrations of substrate allows fungi to respond dynamically to the changing availability of specific resources.

Benefits of exoenzyme production can also be lost after secretion because the enzymes are liable to denature, degrade or diffuse away from the producer cell.

[22] Agricultural practices such as fertilizer amendments and tillage can change the spatial distribution of resources, resulting in altered exoenzyme activity in the soil profile.

[23] Introduction of moisture exposes soil organic matter to enzyme catalysis[24] and also increases loss of soluble monomers via diffusion.

[25][26][27] By adapting their metabolism to the availability of varying amounts of carbon and nitrogen in the environment, fungi produce a mixture of oxidative and hydrolytic enzymes to efficiently break down lignocelluloses like wood.

[38] Most white-rot species also produce laccase, a copper-containing enzyme that degrades polymeric lignin and humic substances.

[39] Brown-rot basidiomycetes are most commonly found in coniferous forests, and are so named because they degrade wood to leave a brown residue that crumbles easily.

[49][50][51] With newer technologies available, molecular methods to quantify abundance of enzyme-coding genes are used to link enzymes with their producers in soil environments.