Secondary Metabolism And Cell Differentiation (molecular Biology, Biochemistry And Biophysics Molekularbiologie, Biochemie Und Biophysik)

1. Secondary Metabolism and Differentiation In addition to the primary metabolic reactions, which are similar in all living beings (formation and breakdown of nucleic acids and proteins as well as of their precursors, of most carbohy­ drates, of some carboxylic acids, etc. ), a vast number of metab­ olic pathways lead to the formation of compounds peculiar to a few species or even to a single chemical race only. These reac­ tions, in accord with CZAPEK (1921) and PAECH (1950), are summed up under the term "secondary metabolism", and their products are called "secondary metabolites. " The wide variety of secondary products formed in nature includes such well-known groups as alkaloids, antibiotics, cardiac glyco­ sides, tannins, saponins, volatile oils, and others. A consider­ able number of them are of economic importance in therapeutics or technology. Although secondary products are produced by micro­ organisms, higher plants, and animals (cf. LUCKNER, 1972), most of the substances are found in the plant kingdom. The lack of mechanisms for true excretion in higher plants may result in this unequal distribution, the "waste products" of metabolism in plants instead being accumulated in the vacuoles, the cell walls, or in special excretory cells or spaces of the organism ("metabolic excretion," cf. FREY-WYSSLING, 1935, 1970; MOTHES, 1966a, b, 1972; LUCKNER et al. , 1976. Many secondary substances have, however, a direct biologic func­ tion. They can be regulatory effectors, e. g. 1. Secondary Metabolism and Differentiation In addition to the primary metabolic reactions, which are similar in all living beings (formation and breakdown of nucleic acids and proteins as well as of their precursors, of most carbohyƯ drates, of some carboxylic acids, etc.), a vast number of metabƯ olic pathways lead to the formation of compounds peculiar to a few species or even to a single chemical race only. These reacƯ tions, in accord with CZAPEK (1921) and PAECH (1950), are summed up under the term "secondary metabolism", and their products are called "secondary metabolites." The wide variety of secondary products formed in nature includes such well-known groups as alkaloids, antibiotics, cardiac glycoƯ sides, tannins, saponins, volatile oils, and others. A considerƯ able number of them are of economic importance in therapeutics or technology. Although secondary products are produced by microƯ organisms, higher plants, and animals (cf. LUCKNER, 1972), most of the substances are found in the plant kingdom. The lack of mechanisms for true excretion in higher plants may result in this unequal distribution, the "waste products" of metabolism in plants instead being accumulated in the vacuoles, the cell walls, or in special excretory cells or spaces of the organism ("metabolic excretion," cf. FREY-WYSSLING, 1935, 1970; MOTHES, 1966a, b, 1972; LUCKNER et al., 1976. Many secondary substances have, however, a direct biologic funcƯ tion. They can be regulatory effectors, e. g Front Matter....Pages I-VI Expression of Secondary Metabolism An Aspect of Cell Specialization of Microorganisms, Higher Plants, and Animals....Pages 1-102 Secondary Metabolism in Cell Cultures of Higher Plants and Problems of Differentiation....Pages 103-123 Back Matter....Pages 125-131