Production of secondary metabolities

Saito, K., Yamazaki, M. and Murakoshi, I. 1992. Transgenic medicinal plants Agrobacterium-mediated foreign gene transfer and production of secondary metabolities. Journal of Natural Products, 55 149-162. 

Herbicides are the biocides most likely to affect the metabolism of plants, including secondary metabolism [107]. The synthesis of hydroxyphenolics and anthocyanin in plants can be influenced by a variety of environmental and chemical stimuli. Some herbicides were found to raise the levels of these compounds in plants [108] whilst others had the opposite effect [109]. The products of secondary metabolism are controlled by enzymes, including PAL and chalcone isomerase (Cl), and several herbicides appear to intensify the activities of those enzymes involved in the accumulation of hydroxyphenolic compounds and anthocyanin biosynthesis in several plant species [109-111] whereas others depress this activity [112]. For example,... 

The chemical reactions common to all living things involve the primary metabolism of the big four we met in Chapter 49—nucleic acids, proteins, carbohydrates, and lipids. Now we must look at chemical reactions that are more restricted. They occur perhaps in just one species, though more commonly in several. They are obviously, then, not essential for life, though they usually help survival. These are the products of secondary metabolism. 

Mycotoxins are products of secondary metabolism of various kinds of filamentous fungi (molds) that produce them as a by-product of metabolism or for defensive purposes. Mycotoxins can have strong toxic, mutagenic, or teratogenic properties and are found in a wide range of agricultural products under different environmental conditions. 

Molds also produce complex products of secondary metabolism. These secondary metabolites include chemicals used to ensure that the molds maintain their niche within their current habitat. These chemicals may suppress the growth of bacteria or other molds (antibiotic effect), or may be toxic to other eukaryotic cells (mycotoxic effect),. Mycotoxins may function as inhibitors of DNA, RNA, and protein synthesis. The production of secondary metabolites... 

By choosing more suitable plant material, root tips, and better nutrient media, excellent results were achieved - first by Gautheret in 1934. Since then, plant cell culture has become a fruitful discipline within biotechnology, with manifold economic potential. This includes the production of various products of secondary metabolism as well as e.g. transgenic crops. 

Medium As discussed in Subheading 2., the most important factor m this respect is probably the medium. There are numerous reports of the way in which the nutrient source affects the secondary metabolism. Such factors include carbon, phosphorus and nitrogen source, levels, and ratios inorganics present m medium levels of aeration/oxygenation the physical state of the medium (liquid or solid). The diversity of metabolism elicited by a range of media should be considered insofar as the biotransformation reactions are a product of secondary metabolism. 

Secondary metabolism is, by contrast, chemistry less fundamental to the workings of life and restricted to smaller groups of organisms. Later in this chapter you will meet alkaloids produced by some plants and terpenes produced by others. Humans produce neither of these, but we do make steroids, as do other animals (and a few plants). All of these molecules are the products of secondary metabolism. 

During the last decade, the progress in the study of secondary metabolism has been chiefly due to the extensive research on enzymes of biosynthetic pathways that yield secondary products. These enzymes include those catalyzing the formation of precursors or products of secondary metabolism. In addition, a number of anaplerotic enzymes ensuring the course of these reactions has also been mentioned (1). 

The principal advantages of this type of cyclic system with transient operating techniques are apparent in bioprocesses whose maximum productivity is in a transient region. The products of secondary metabolism (Pirt, 1974) are a typical example of this group of processes. Another group consists of processes whose optimal operation requires an optimal substrate concentration— biomass production with bakers yeast, for example (Aiba et al., 1976)—or where the process is subject to substrate inhibition. An important area of application for this is in biological waste water purification. These periodic modes of operation generally show increased productivity. More systematic and detailed study is needed in this area. 

The CPFR has distinct advantages for those bioprocesses that call for a specific reaction time, as illustrated in Fig. 6.27. Examples of such processes include the formation of the products of secondary metabolism, sterilizations to destroy cells and spores, and the high temperature treatment of foodstuffs. 

Piepersberg W, Distler J. Aminoglycosides and sugar components in other secondary metabolites. Rehm H-J, Reed G, Piihler A. Stadler P, eds. Biotechnology, 2nd ed., Vol, 7, Products of Secondary Metabolism. Weinheim VCH, 1997 (in press). 

Yoshimura I, Kurokawa T, Nakano T, Yamamoto Y (1989) Production of secondary metabolic substances by cultured tissues of Usnea flexilis. Bull Kochi Gakuen J Coll 20 535-540... 

Phenolic compounds from plant sources, termed as phenolic phytochemicals, are widespread natural components in our diet, and are being targeted for dietary management of chronic disease and have relevance in alternative medicine. Phenolic phytochemicals are compounds which are products of secondary metabolism in plants and constitute one of the most abundant compounds of metabolites in the plant kingdom (Naczk... 

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