Metabolic labeling comparison

The only other oxime on which any metabolic information was found is III. Way jet al. perfused III labeled with In the 1 and 3 positions of the 3-carbon chain between the pyrldinlum moieties through isolated rat livers. The only metabolite that they reported finding in the perfusate was l-(4-aldoximinopyridinium)-3-(4-cyano-pyridinium) propane ion, which was Identified by comparison with the authentic synthetic compound. Later, DeMiranda et al. O found the same compound as the principal metabolite in the urine of rats that hed been given doses of III. Ill seems to be treated metabolically as though it were one molecule of 2-PAH attached to a large Inert group. 

Dichlorophenpxy) acetic acid-14C is metabolized by plant tissue to inactive, water-soluble substances, some of which regenerate the parent acid on hydrolysis. The rate of metabolism differs with different species, but is usually low in comparison with the indole or naphthalene auxins. One of the earlier studies described a single major metabolite in corn, wheat, peas, and tomatoes,121 the identity of which is still uncertain. In another study of differences between species which were susceptible and those which were resistant to the herbicide, the resistant red currant metabolized 50% of the carboxyl-labeled and 20% of the methylene-labeled (2,4 dichlorophenoxy)acetic acid to 14COi in seven days, whereas the susceptible black currant altered122 only 2%. Similar effects were found with apple varieties. Strawberry and lilac decarboxylated the herbicide readily however, 16 other species, of various susceptibilities to herbicide, were unable to decarboxylate the acid to any significant extent. In both varieties of currant, 5 to 10% of the herbicide was converted into water-soluble derivatives of the parent acid, and 10 to 30% was bound in the leaf tissue in an unextractable form. 

In all studies thus far made on starch synthetase, the incorporation of D-glucose from a D-glucosyl ester of a nucleotide into an acceptor molecule has been made by using a radioactively labeled D-glucosyl group in the nucleotide ester, and so the results are unambiguous. However, the extent of the incorporation of D-glucose into the acceptor was very low in the early experiments, and the view has been expressed that starch synthetase is not the major pathway for metabolism of starch. This conclusion seems very reasonable starch biosynthesis is probably a multi-pathway process. Of interest in this connection is a comparison that has been made of starch synthetase activity in non-waxy and waxy maize and rice. ... 

Salonen J S, Suolinna E M 1988 Metabolism of detomidine in the rat. I. Comparison of H-labelled metabolites formed in vitro and in vivo. European Journal of Drug Metabolism and Pharmacokinetics 13 53-58 Salonen J S, Vaha-Vahe T, Vainio O et al 1989 Single-dose pharmacokinetics of detomidine in the horse and cow. Journal of Veterinary Pharmacology and Therapeutics 12 65-72... 

Figure 1 The retrobiosynthetic principle. Labeling patterns of central metabolic intermediates (shown in yellow boxes) are reconstructed from the labeling patterns of sink metabolites, such as protein-derived amino acids, storage metabolites (starch and lipids), cellulose, isoprenoids, or RNA-derived nucleosides. The reconstruction is symbolized by retro arrows following the principles of retrosynthesis in synthetic organic chemistry. The figure is based on known biosynthetic pathways of amino acids, starch, cellulose, nucleosides, and isoprenoids in plants. The profiles of the central metabolites can then be used for predictions of the labeling patterns of secondary metabolites. In comparison with the observed labeling patterns of the target compounds, hypothetical pathways can be falsified on this basis.

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