ABSTRACT
Primary metabolism may be contrasted with other metabolic pathways in which the intermediates of primary metabolism are not used for growth but are involved in a variety of peculiar “secondary” pathways, many of which produce highly unusual, even bizarre, end products. Secondary metabolites are largely produced by anabolic routes, and their synthesis consumes energy and reducing power generated from primary metabolism. Attempts to use secondary metabolites as “chemical signatures” to aid in taxonomy have been only partially successful. The impetus to study secondary metabolites has come from several disciplines and from both basic and applied science. Most of the basic research has been conducted by organic chemists, who usually call secondary metabolites “natural products.” Filamentous fungi and yeasts possess highly ordered, multilayered cell walls. Protoplast technology has been applied to several economically important fungal metabolites both to obtain cell-free systems and to overcome permeability problems that sometimes influence precursor feeding studies.
