Biosynthetic effects

Schouten, S., Klien, W.C.M., Breteler, K., Blokker, P., Schogt, N., Irene, W., Rupstra, I.C., Grice, K., Bass, M., and Damste J.S.S. (1998) Biosynthetic effects on the stable carbon isotopic compositions of algal lipids Implications for deciphering the carbon isotopic biomarker record. Geochim. Cosmochim. Acta 62, 1397-1406. 

The provision of an appropriate fatty acid pool for use in synthesis of phospholipids involves a complex mixture of dietary and biosynthetic effects. To at least some extent, one is what one eats applies in the context of adaptation of lipid-containing structures, a point... 

As will be evident from studies on induced biosynthetic effects (Section 5), sulfation of glycosaminoglycans can be blocked selectively, but this does not seem to exert a feedback control since polysaccharide synthesis can still continue without sulfation. It would therefore seem unnecessary for the living system to provide a control at this stage, but that the system can adapt to variations in sulfate availability by use of the alternative, but not normal, sulfation route of sulfation after polymerization of the carbohydrate. 

Examples of the use of induced biosynthetic effects for the deduction of the processes involved include the use of puromycin and cyclohexi-mide. These compounds, according to experiments with other systems, inhibit protein synthesis. Thus the inhibition of biosynthesis of hyaluronic acid and dermatan sulfate in human fibroblast cultures (M13, M16), of hyaluronic acid in synovial cells (S31), and of chondroitin sulfate (HI) led to the conclusion that the synthesis of protein acceptor is necessary for the polysaccharide chain initiation. Comparison of the effects of 1-butanol on the biosynthesis of chick cartilage chondroitin sulfate and streptococcal hyaluronic acid led to the suggestion that binding of Mg + ions and the uridine diphosphate moiety results in stabilization of the spatial arrangement of the specific enzymes (S47, T4). 

The traditional p/s ratio and now the n-6/n-3 PUFA ratio may be of little value because they fail to recognize the multiple effects of dietary PUFA and their metabolic interrelationships. In a multivariate system, attempts to describe a ratio of two variables have little meaning and are an inappropriate description of a mixture of fatty acids having a multiplicity of biosynthetic effects. These values should therefore be considered only as possible targets. It should be no longer valid to base dietary recommendations on the attainment of plasma... 

Carotenoids absorb visible light (Section 13 21) and dissipate its energy as heat thereby protecting the organism from any potentially harmful effects associated with sunlight induced photochemistry They are also indirectly involved m the chemistry of vision owing to the fact that p carotene is the biosynthetic precursor of vitamin A also known as retinol a key substance m the visual process... 

A number of the genes involved in the biosynthesis of thiamine in E. coli (89—92), i hium meliloti (93), B. suhtilis (94), and Schi saccharomycespomhe (95,96) have been mapped, cloned, sequenced, and associated with biosynthetic functions. Thiamine biosynthesis is tightly controlled by feedback and repression mechanisms limiting overproduction (97,98). A cost-effective bioprocess for production of thiamine will require significant additional progress. 

The overall biosynthetic pathway to the tetracychnes has been reviewed (74). Studies (75—78) utilising labeled acetate and malonate and nmr analysis of the isolated oxytetracycline (2), have demonstrated the exclusive malonate origin of the tetracycline carbon skeleton, the carboxamide substituent, and the folding mode of the polyketide chain. Feeding experiments using [1- 02] acetate and analysis of the nmr isotope shift effects, led to the location of... 

Kinetic isotope effects are an important factor in the biology of deuterium. Isotopic fractionation of hydrogen and deuterium in plants occurs in photosynthesis. The lighter isotope is preferentially incorporated from water into carbohydrates and tipids formed by photosynthesis. Hydrogen isotopic fractionation has thus become a valuable tool in the elucidation of plant biosynthetic pathways (42,43). 

Use of biochemical and biological information for bioprocesses is also significant to the advancement of BRE. Here, the information on the signal transduction from external Ca was utilized for regulation of ginsenoside biosynthetic pathway of cultured cells of P. notoginseng. A quantitative study on the effects of external calcium and calcium sensors was conducted to... 

As noted, the alkaloid yield from the Beocin plants was low, which the authors suggested might be caused by the poor soil in which the plants were growing (Popovic et ah, 1992). One could ask whether the soil conditions to which they refer might be influential in the overall alkaloid biosynthetic processes in this species. It would be of interest to see experimental studies aimed at determining the effect of soil components on these processes. In the present case, it may be a lack of, or reduction in the activity of, the oxidase(s) necessary for the dimerization process (required to form the bibenzyldihydroisoquinolines) to occur. It is also possible that the lack of dimeric alkaloids may simply reflect a concentration effect caused by the edaphic conditions. These questions should be accessible to experiment. 

Little is known of how the biosynthetic metabolon is assembled, what mechanisms control the membrane-specific targeting, and how the conversions to apocarotenoids occur. Yet the current approach to drive import of bacterial or plant genes is to use transit sequences of a stromal protein that may limit the effectiveness of the transgene. In addition, for specific applications of controlling carotenoid composition, we need to better understand the interactions of the various enzymes,... 

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