Abstract
An S-adenosyl-l-methionine (SAM): cytisine N-methyltransferase could be demonstrated in crude enzyme preparations from Laburnum anagyroides plants and cell cultures of L. alpinum and Cytisus canariensis. The transferase specifically catalyzes the transfer of a methyl group from SAM to cytisine. The apparent Km values are 60 μmol l-1 for cytisine and 17 μmol l-1 for SAM. Other quinolizidine alkaloids, e.g. angustifoline and albine, are N-methylated by only 10–15%. The transferase shows a pH optimum at pH 8.5. It is activated by dithioerythritol and inhibited by thiol reagents and Fe2+ and Fe3+. The reaction product S-adenosylhomocysteine is a powerful inhibitor of the transferase reaction. Cell cultures of L. alpinum which have an active SAM: cytisine N-methyltransferase and which are able to N-methylate exogenous cytisine in vivo, do not accumulate cytisine or N-methylcytisine to a detectable degree.
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Abbreviations
- GLC:
-
gas-liquid chromatography
- SAM:
-
S-adenosylmethionine
- TLC:
-
thin-layer chromatography
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Wink, M. N-Methylation of quinolizidine alkaloids: an S-adenosyl-l-methionine: cytisine N-methyltransferase from Laburnum anagyroides plants and cell cultures of L. alpinum and Cytisus canariensis . Planta 161, 339–344 (1984). https://doi.org/10.1007/BF00398724
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DOI: https://doi.org/10.1007/BF00398724