Implication of tyramine in the biosynthesis of morphinan alkaloids in Papaver |
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Authors: | Margaret F Roberts Toni M Kutchan Richard T Brown Carmine J Coscia |
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Institution: | (1) Department of Pharmacognosy, London University, WCIN 1AX London, UK;(2) Department of Biochemistry, St. Louis University School of Medicine, 63104 St. Louis, MO, USA;(3) Department of Chemistry, The University, M13 9PL Manchester, UK |
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Abstract: | Doubly-labeled 3H, 14C]tyrosines, 1-13C-]tyramine or 2-14C]tyramine, administered to the stems of intact Papaver somniferum L. plants, were found to be incorporated into the morphinan alkaloids of the plant with comparable efficiency. 3H/14C ratios of alkaloids from plants fed the tyrosines were consistent with an almost equal conversion of this amino acid into the tetrahydroisoquinoline (TIQ) and benzyl-derived segments. Nuclear magnetic resonance (NMR) analyses of morphine isolated after administration of 1-13C]tyramine demonstrated selective labeling of C-16 of the alkaloid, indicating the conversion of this amine primarily into the TIQ-derived moiety. Morphine and thebaine labeled by 2-14C]tyramine were degraded to phenanthridines and N,N-dimethyl ethylamines. Of the total radioactivity in the alkaloids 97% was found to be associated with the ethylamines, a distribution consistent with the NMR data. This preferential utilization of tyramine in the biosynthesis of morphinan alkaloids can be explained by the compartmentalization of intermediates and enzymes of the pathway.Abbreviations
L-dopa
L-3,4-dihydroxyphenylalanine
- HPLC
high-pressure liquid chromatography
- NMR
nuelear magnetic resonance
- TIQ
tetrahydroisoquinoline |
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Keywords: | Tyramine-morphinan Alkaloid biosynthesis Papaver (alkaloids) Tyrosine |
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