Plant cultures, metabolism

Plant. Fewer and Owen (1989) found 3,5,6-trichloro-2-pyridinol as the major metabolite in plants. Cultured soybean cells metabolized triclopyr to dimethyl triclopyr-aspartate and dimethyl triclopyrglutamate which can be rehydrolyzed to form the parent compound. 

Runguphan W, O Connor SE. (2009) Metabolic reprogramming of periwinkle plant culture. Nat Chem Biol 5 151-153. 

Plant species that produce many small seeds usually do not invest in toxins, whereas species with few nutrient-rich seeds generally do (18, 22). The knowledge about these adaptations is valuable if we think of manipulating plant secondary metabolism, for example in plant cell cultures, to produce economically important natural products. 

Carbon source was found to be a significant factor in plant cell metabolism [34 - 39], which affected the accumulation of alkaloids by suspension cultures of Holarrhena antidysenterica [36], of anthocyanins by Vitis vinifera cell suspen-... 

In plant cells, a peroxidase activity showed to be correlated with the ability of plant cultures to metabolize PCBs. Nevertheless, as mentioned above in fungal cultures, no correlation of manganese- and lignin-peroxidase activities with PCB degradation was found [131]. 

Oksman-Caldenty KM, Arroo R. Regulation of tropane alkaloid metabolism in plants and plant cell cultures. In Metabolic Engineering of Plant Secondary Metabolism. Verpoorte R, Alfermann AW, eds. 2000. Kluwer Academic Publishers, Dordrecht, the Netherlands, pp. 253-281. 

Biosynthetic study of plant secondary metabolism which can lead to a stable and good supply of desired constituents is very important particularly for medicinal plants. Plant tissue cultures (both cells and organized cultures) have been successfully applied to several medicinal plants and resulted in the successful production of some useful secondary metabolites such as alkaloids and terpenoids. Recendy, in some solanaceous plants (Atropa belladonna etc), the artificial improvement of tropane alkaloid metabolism, directed at the high production of scopolamine, has been tried by Agrobacterium-mediited gene transfer (100). However, for the production of phenolics, especially for polyphenols in medicinal plants, sufficient research has not been carried out on tissue cultures and only cell suspension cultures have been usually employed. 

The initial enthusiasm for tapping the vast synthetic potential of cultured plant cells has largely given way to the realization that much needs to be learned about the biochemical and genetic regulation of plant secondary metabolism before cost-effective, industrial-scale production becomes feasible. 

Most xenobiotic GSH conjugates In plants are metabolized at least to cysteine conjugates and cysteine conjugates appear to be the pivotal point In metabolism. Cysteine conjugates may be end-products of metabolism, as observed In methldathlon metabolism In tomato and peanut cell suspension culture, or aclfluorfen metabolism In soybean and peanut cell suspension culture (16). Xenobiotic cysteine conjugates are frequently N-acylated with malonic acid as shown In Equation 25. This was demonstrated with the following... 

A GST enzyme from pea Is very effective In catalyzing GSH conjugation of the herbicide fluorodlfen ( ). This enzyme has a pH optimum and other properties that are comparable to mammalian GST enzymes (85). This enzyme activity was observed In other plant species, but fluorodlfen resistant species appeared to have higher levels of this enzyme than susceptible species ( ). Additional studies with pea Indicated the presence of two soluble GST Isozymes, one that utilized fluorodlfen and one that utilized -cinnamic acid as substrates (W7). These Isozymes appeared to form aggregates during purification. In addition, a microsomal GST was detected In pea that utilized both -cinnamic acid and benzo(a)pyrene as substrates (WT.). Soybean cell suspension cultures metabolized -clnnamlc acid In a 6% yield to a product that corresponded to the GSH conjugate of t-clnnamlc acid by paper chromatography (107). 

No direct comparison with whole plants made. Metabolism was species dependent in cell cultures. Hydroxylation occurred in poppy and sugarbeet, but chloridazon was not metabolized in mung bean, soybean, tobacco, or parsely. 

Quite a few plant enzymes find commercial application, e.g. proteases, glycosidases and peroxidases. Most of these enzymes function in plant primary metabolism. The enzymes from plant secondary metabolism show interesting features with respect to substrate (non-)specificity and the broad range of reactions catalyzed. However, the limited availability of these enzymes hampers further exploitation. Alternatively, plant enzymes can often be extracted with more ease and better yields from plant cell cultures as compared to the intact plants. Cell culture material can be easily obtained in sufficient amounts, furthermore it is often possible to increase the activity of the enzyme in these cells by induction. 

Plant cell culture is becoming a widely used technology for the production of plant biochemicals and also for the biotransformation of pharmaceuticals. The dangers posed to exposed workers by this technology will be entirely dependent on the products of these processes and possibly the by-products of the plant cells metabolism. Therefore the hazards of plant cell culture will probably be similar to those of animal cell culture discussed above. 

Bernhardt P, McCoy E, O Connor SE (2007) Rapid identification of enzyme variants for reengineered alkaloid biosynthesis in periwinkle. Chem Biol 14 888-897 Runguphan W, O Connor SE (2009) Metabolic reprogramming of periwinkle plant culture. Nat Chem Biol 5 151-153... 

The term elicitor refers to chemicals from various sources, biotic or abiotic, as well as physical factors, that can trigger a response in living organisms resulting in a high accumulation of secondary metabolites. Therefore, elicitors are usefiil tools for improving the production of plant valuable compounds ([36] and references therein). The effectiveness of elicitation as a tool to enhance the production of secondary metabolites depends on a complex interaction between the elicitor and the plant cell. There is evidence that the same elicitor can stimulate secondary metabolism in different cell cultures and that certain plant cultures are responsive to diverse elicitors. Treatment of a particular plant cell culture with different elicitors will result in the accumulation of a particular class of compounds, since these are specific of each plant culture. Although the class of metabolite depends on the plant species, the kinetics of induction or accumulation levels can vary with different elicitors. 

Heintz, R., and P. Benveniste Plant Sterol Metabolism. Enzymatic Cleavage of the 9p,19p-Cyclopropane Ring of Cyclopropyl Sterols in Bramble Tissue Cultures. J. Biol. Chem. 249,4267 (1974). 

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