Xenobiotic metabolism plants

At least two well-documented cases of plant xenobiotic metabolism to N-O-glucosides have been reported (, ). Oxamyl insecticide was converted to an N-0-glucoslde in tobacco, young peanut plants, alfalfa, and the fruit of orange and tomato ( ) (Equation 6). This... 

Egaas, E., J.U. Skaare, N.O. Svendsen, M. Sandvik, J.G. Falls, W.C. Dautennan, T.K. Collier, and J. Netland. 1993. A comparative study of effects of atrazine on xenobiotic metabolizing enzymes in fish and insect, and of the in vitro phase II atrazine metabolism in some fish, insects, mammals and one plant species. Comp. Biochem. Physiol. 106C 141-149. 

Fujisawa T, Matoba Y, Katagi T (2009) Application of separated leaf cell suspension to xenobiotic metabolism in plant. J Agric Food Chem 57 6982-6989... 

Scheline, R.R., Mammalian Metabolism of Plant Xenobiotics, Academic Press, London, 1978. 

Reid, P.C., Chen, T.T. Insect Blochem. 1981, 11, 297-305. Schellne, R.R. "Mammalian Metabolism of Plant Xenobiotics," Academic Press, New York, 1978. 

R. R. Scheline, in Mammalian Metabolism of Plant Xenobiotics , Academic... 

Comparative biochemistry. Some researchers believe that the proper role of comparative biochemistry is to put evolution on a molecular basis, and that detoxication enzymes, like other enzymes, are suitable subjects for study. Xenobiotic-metabolizing enzymes were probably essential in the early stages of animal evolution because secondary plant products, even those of low toxicity, are frequently lipophilic and as a consequence would, in the absence of such enzymes, accumulate in lipid membranes and lipid depots. The evolution of cytochrome P450 isoforms, with more than 2000 isoform cDNA sequences known, is proving a useful tool for the study of biochemical evolution. 

Metabolism is a complex and fascinating process. It is extremely useful in getting rid of bodily toxicants. Apart from all of the toxicants in the man-made environment around us, even animal and plant food contains many chemicals that have no nutritional value but do have potential toxicity. If these chemicals are sufficiently lipid-soluble, they will reach the blood, and they will not be readily excreted unless they are converted to more water-soluble metabolites. This may be the reason why all animals have a wide variety of xenobiotic-metabolizing enzymes that convert a wide range of chemical structures to water-soluble metabolites that can be excreted in urine (Mulder, 2006). 

Fonne-Pfister, R., Simon, A., Salaun, J.P., and Durst, F., Xenobiotic metabolism in higher plants. Involvement of microsomal cytochrome P-450 in aminopyrine N-demethylation, Plant Sci., 55, 9-20, 1988. 

The study of xenobiotic metabolism has developed rapidly during the past few decades. These studies have been fundamental in the assessment of drug efficacy, safety, and design of dosage regimens in the development of food additives and the assessment of potential hazards of contaminants in the evaluation of toxic chemicals and in the development of pesticides and herbicides and their metabolic fate in insects, other animals, and plants. The metabolism of many xenobiotics is fundamental to many toxic processes such as carcinogenesis, teratogenesis, and tissue necrosis. Often the same enzymes involved in... 

In this review, conjugation reactions utilized In xenobiotic metabolism In plants will be discussed In reference to functional groups, phase I reactions necessary to produce a functional group suitable for conjugation, relative rates of reactions, competing metabolic pathways, frequency of occurence, plant species, stability of conjugates, and the relationship between metabolism and herbicide selectivity. Pesticides discussed herein are listed In Table I. 

Table V. Xenobiotics Metabolized to Glucose Esters In Plants ...

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... 

Isomerization of an S-cystelne conjugate to an -cysteine conjugate via the Smiles rearrangement has been observed In the metabolism of two trlazlne xenobiotics In higher plants atrazlne metabolism In sorghum (103,W ) 8 dlmethametryn metabolism In rice (J05). This nonenzymatic rearrangement (Equation 26) has not... 

These malonyltransferases should be subjected to detailed substrate specificity studies to assess their potential role In xenobiotic metabolism In plants. 

Improved methods and instrumentation for metabolite isolation and identification, such as capillary GC, GC/MS, HPLC, high field NMR, FAB/MS, CI/MS, FT-IR and HPLC/MS have made the identification of new or unusual metabolites more practical. As these advanced techniques are employed to study xenobiotic metabolism in more diverse species of plants, additional classes of xenobiotics will no doubt be discovered. 

Although not a plant xenobiotic conjugate, the metabolism of the glycine conjugate of salicylic acid In Isolated perfused rat kidney has been studied (22). The authors were surprised that 20-30% of the dose was hydrolyzed to salicylic acid In that organ, whereas In parallel experiments the liver did not posses this activity. 

The major function of xenobiotic metabolism is the elimination of physiologically useless compounds, some of which may be harmful wimess the many toxins produced by plants. This evolutionary function justifies the designation of detoxification originally given to reactions of xenobiotic metabolism. However, numerous xenobiotics and even a marked number of drugs are known to yields toxic... 

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