Fungal Secondary Metabolism

Abstract

Secondary metabolites (SMs) are low molecular-weight compounds derived from primary metabolites via specialized pathways and are produced mainly by microorganisms and plants. Fungi produce a huge number and variety of SMs, many of which have interesting biological activities. SMs can provide self-protection and may act as mediators for communication with other organisms or as virulence factors for plant and animal pathogens. Moreover, they serve as defense molecules against other microbes (antibiotics), thus contributing to the organization of microbial consortia. Fungal SMs are grouped as families (polyketides and fatty acids; terpenoids and steroids; phenylpropanoids; alkaloids; specialized amino acids and peptides) of closely related compounds resulting from biosynthetic enzymes less specific to their substrate than those of primary metabolism. The central part of a secondary metabolism gene cluster typically codes for a backbone-generating enzyme such as polyketide synthase (PKS), non-ribosomal peptide synthetase (NRPS), hybrid NRPS-PKS, dimethylallyl tryptophan synthase, or terpene cyclase. PKS and NRPS core enzymes consist of multiple domains that progressively assemble the metabolite backbone. Fungal secondary metabolism is regulated by a complex network of signals, some of them activated as a response to certain nutritional or environmental stimuli. In this article the biochemistry, the biological impact, the fungal genes involved in SM biosynthesis and their regulation have been described.