Metabolite translocation

The amount of chloroform-soluble C in the roots of peanut plants grown in hydroponics decreased greatly as a function of time. After 33 days, chloroform soluble C accounted for only 5 of the 14C in the roots. This was probably due to metabolism of the remaining PCNB, volatilization of some metabolites, translocation to foliar tissue, and additional metabolism of nonpolar metabolites to polar metabolites or Insoluble residue. Because of volatility, it is possible that chloroform-soluble... 

The observed ozone-induced growth reductions of roots could result from (a) a direct toxic effect of ozone on the root, (b) an ozone modification of the foliage metabolism which alters the quantity and/or quality of metabolites translocated to the roots, or (c) an alteration in soil chemistry. 

Methylthio turnover could be responsible for the high residues of pentachlorothioanisole and bis(methylthio)tetrachlorobenzene found in mussels gathered around the estuary of the river Rhine (82). These residues could result from the metabolism of pentachloronitrobenzene or hexachlorobenzene in the MAP in some species upstream, and the resultant methylthio-containing metabolites translocated downstream undergoing GSH-mediated methylthio-turnover in various species, the end result being an apparent bioaccumulation. 

Fig. 1 gives a schematic presentation of the known mitochondrial metabolite translocators together with the main metabolic processes in which they are involved. 

Fenn, L. B., and Feagley, S. (1999). Review of Beneficial Uses of Calcium and Ammonium Salts for Stimulating Plant Growth and Metabolite Translocation. Commun. Soil Set Plant Anal. 39(19/20), 2627-2641. 

Plant metabolism studies will provide information on the absorption, translocation, dissipation and degradation of the agrochemical. This information defines the residual analytes of regulatory concern that could include either the parent compound or metabolites in the field crops. Plant metabolism studies should be conducted with at least three crop representatives of three different crop groups listed in Table 1. One of the major objectives is to determine the comparative metabolism of the agrochemicals between animals and plants among different plant species. MAFF approves metabolism studies that are conducted in foreign countries, which should be operated under the certified GLP system. 

Dinitroaniline herbicides show minimal plant systematic translocation properties with the majority of the absorbed residues in the root tissues. Metabolites identified include traces of Al-dealkylation, alkyl and aryl hydroxylation and nitro reduction products. Low levels of dinitroaniline herbicide residues have been reported in raw agricultural commodities according to Good Agricultural Practice. 

Fenvalerate is not significantly absorbed or translocated in plants. Cotton, apples, and lettuce treated with fenvalerate contained surface residues of parent fenvalerate 8 weeks after treatment (Reed 1981). In addition to the parent compound, which accounted for 80% of all residues, identified metabolites included 3-phenoxybenzaldehyde, 3-phenoxybenzyl methylbutyric acid, and conjugates of these compounds. Half-time persistence of fenvalerate on plant surfaces is between 2 and 4 weeks, and degradation is primarily a result of weathering (Reed 1981). 

Translocate conjugated PAH metabolites to the gall bladder prior to excretion in feces and urine... 

Russell BD, Elsdon TS, Gillanders BM, Connell SD (2005) Nutrients increase epiphyte loads broad-scale observations and an experimental assessment. Mar Biol 147 551-558 Schmitt TM, Hay ME, Lindquist N (1995) Constraints on chemically mediated coevolution multiple functions for seaweed secondary metabolites. Ecology 76 107-123 Schmitz K, Lobban CS (1976) Survey of translocation in Laminariales (Phaeophyceae). Mar Biol 36 207-216... 

The metabolites are transformed and translocated by reactions and transport processes, both modified by allosteric regulation. 

For the irreversible reactions, we assume Michaelis Menten kinetics, giving rise to 15 saturation parameters O1. C [0, 1] for substrates and products, respectively. In addition, the triosephospate translocator is modeled with four saturation parameters, corresponding to the model of Petterson and Ryde-Petterson [113]. Furthermore, allosteric regulation gives rise to 10 additional parameters 7 parameters 9" e [0, — n for inhibitory interactions and 3 parameters 0" [0, n] for the activation of starch synthesis by the metabolites PGA, F6P, and FBP. We assume n = 4 as an upper bound for the Hill coefficient. 

Plant. Endosulfan sulfate was formed when endosulfan was translocated from the leaves to roots in both bean and sugar beet plants (Beard and Ware, 1969). In tobacco leaves, a-endosulfan is hydrolyzed to endosulfan diol (Chopra and Mahfouz, 1977). Stewart and Cairns (1974) reported the metabolite endosulfan sulfate was identified in potato peels and pulp at concentrations of 0.3 and 0.03 ppm, respectively. They also reported that the half-life for the conversion of a-endosulfan to P-endosulfan was 60 d. 

Plant. Oat plants were grown in two soils treated with [ CJparathion. Less than 2% of the applied [ CJparathion was translocated to the oat plant. Metabolites identified in both soils and leaves were paraoxon, aminoparaoxon, aminoparathion, p-nitrophenol, and an aminophenol (Fuhremann and Lichtenstein, 1980). 

Plant Diaziuou was rapidly absorbed by and translocated in rice plants. Metabolites identified in both rice plants and a paddy soil were 2-isopropyl-4-methyl-6-hydroxypyrimidine (hydrolysis product), 2-(l -hydroxy-l -methyl)ethyl-4-methyl-6-hydroxypyrimidine, and other polar compounds (Laanio et al, 1972). Oxidizes in plants to diazoxon (Laanio et al., 1972 Ralls et al, 1966 Wolfe et al., 1976) although 2-isopropyl-4-methylpyrimidin-6-ol was identified in bean plants (Kansouh and Hopkins, 1968) and as a hydrolysis product in soil (Somasundaram et al., 1991) and water (Suffet et al., 1967). Five d after spraying, pyrimidine ring-labeled C-diazinon was oxidized to oxodiazinon which then hydrolyzed to 2-isopropyl-4-methylpyrimidin-6-ol which, in turn, was further metabolized to carbon dioxide (Ralls et al, 1966). Diazinon was transformed in field-sprayed kale plants to hydroxydiazinon 0,0-diethyl-0-[2-(2 -hydroxy-2 -propyl)-4-methyl-6-pyrimidinyl] phosphorothioate which was not previously reported (Pardue et al., 1970). 

---