Precursor supply

Metabolic Engineering for Enhancing Precursor Supply for Isoprenoid Production... 

The alcohol evaporation under vacuum, the treatment of cells and microcapsules by silica precursor supplied by gas carrier and infiltration of silica nanoparticles, whose are discussed above, are the examples of such modified approaches. There are two original methods whose would be well to consider. 

These results confirmed that branched-chain amino acid catabolism via the BCDH reaction provides the fatty acid precursors for natural avermectin biosynthesis in S. avermitilis. In contrast, B. subtilis appears to possess two mechanisms for branched-chain precursor supply. The dual substrate pyruvate/branched-chain a-keto acid dehydrogenase (aceA) and an a-keto acid dehydrogenase (bfmB), which also has some ability to metabolize pyruvate, appears to be primarily involved in supplying the branched-chain initiators of long, branched-chain fatty acid biosynthesis [32,42], Two mutations are therefore required to generate the bkd phenotype in B. subtilis [31,42],... 

Because these genes are often arranged in clusters, this has allowed a combinatorial biosynthetic approach for the construction of diverse libraries of polyketides and nonribosomal peptides.388387 The use of E. coli as a production host whereby precursor supply and selected pathway enzymes are modified has resulted in respectable titers of targeted compounds as well as novel derivatives.388393... 

Lythraceae Alkaloids.—Cryogenine (18) has been shown to incorporate [3- " C]-phenylalanine in Heimia salicifolia. Oxidative degradation established the incorporation of labels at the positions shown in (18) the difference in incorporation of the two units may be a function of the stage at which they normally enter the biosynthetic pathway. Although ring d and the whole of its C3 side chain are probably derived from phenylalanine, it is not yet clear whether this precursor supplies three or only one carbon atom of the quinolizidine system. 

Metabolic Pathway Engineering to Improve Riboflavin Precursor Supply 127... 

Figure 8.4 Biosynthetic potentiai of Pseudomonas putida. Extended carbon core metabolism of Pseudomonas putida KT2440 including the major catabolic routes of Entner-Doudoroff pathway, Embden-Meyerhof-Parnas pathway, pentose phosphate pathway, tricarboxylic acid cycle, glyoxylate shunt, anaplerotic reactions, fatty acid de novo biosynthesis, p-oxidation of fatty acids, as well as the convergent -ketoadipate pathway for catabolism of aromatics. Known pathways for respective precursor supply for the broad product spectrum of P. putida KT2440 are indicated by light red arrows. Natural products and substrates are highlighted in black, heterologous products and substrates In red.

The development of plant cell culture techniques has facilitated major breakthroughs in the study of the biosynthesis of plant secondary compounds (Barz and Ellis, 1981 Ellis, 1988 Flores, 1987 Hutchinson, 1986 Wink, 1987). Nonetheless, many cultures either do not produce secondary metabolites or produce an array that difiers from that found in the plant. Thus, there are still many questions to be answered. In instances where a culture fails to produce a particular chemical, it is often assumed that the enz)mies of the pathway are not formed, but, sometimes, only one enzyme is repressed or there is no product formation because of poor precursor supply, lack of storage capacity, or product degradation (Wink, 1987). The addition of exogenous precursors to the culture medium may increase product yield. For example, many plants appear to contain an L-alanine aldehyde aminotransferase that results in amine formation the supply... 

The use of purified enzymes or purified organelles for the study of lipid metabolism in plants satisfies a desire for tidiness. The substrates can be purified, and the reaction to be studied can be isolated from preceding, subsequent, and competing reactions. In vitro experiments, however, do not provide us with an understanding of the interrelationship of different lipid molecules and different organelles. Experiments with simple precursors supplied to intact tissues are much more complicated to interpret, but they help to check whether in vitro results are physiologically relevant. These results with tissues also illustrate the variability in different plants. 

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