Extracellular enzymes that degrade biopolymers are one of the defining features of saprobic basidiomycetes, and are a selective advantage in the environments of these species. They utilize dead organic matter that is mainly composed of cell wall polysaccharides and other biopolymers, including cell wall polymers of plant origin (cellulose, hemicelluloses, lignin, pectin), cell wall polysaccharides of fungi (chitin) and nutrient reserve polysaccharide (starch) as well as proteins. Decomposition of some biopolymers, cellulose, starch and hemicelluloses provides carbon and energy for growth, while others—most notably lignin—have to be degraded only to get access to other substrates. Since the decomposition of proteins (that serve as an easily available source of carbon and nitrogen) is widespread among many organisms, the landmarks of the saprotrophic lifestyle are the extracellular enzymes that degrade nonprotein biopolymers.

Extracellular enzyme production has only been studied in detail in two ecological groups of saprotrophic basidiomycetes, wood-rotters and soil-inhabiters. This chapter will focus on the enzymes produced by these basidiomycetes and on their involvement, roles and occurrence in the environment.

0 0

Post a comment