Biosynthesis of a retrochalcone,echinatin: Involvement of O-methyltransferase to licodione |
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Authors: | Shin-Ichi Ayabe Takafumi Yoshikawa Miyuki Kobayashi Tsutomu Furuya |
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Affiliation: | School of Pharmaceutical Sciences, Kitasato University, Minato-ku, Tokyo 108, Japan |
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Abstract: | In order to clarify the O-methylation step in the biosynthesis of a retrochalcone, echinatin(4,4′-dihydroxy-2-methoxychalcone), methyl transfer from S-adenosyl-l-methionine (SAM) to licodione (1-(2,4-dihydroxyphenyl)-3-(4-hydroxyphenyl)-1,3-propanedione) in the cell-free extract of the cultured cells of Glycyrrhiza echinata was examined. Time course of methyl transferring activity during culture cycle in 4 strains was correlated to echinatin content. The enzyme catalysing this reaction, licodione O-methyltransferase (LMT), was purified 135-fold. Substrate specificity studies implied that the hydroxy group ortho to the C3 linkage in licodione was methylated in this reaction. O-Methyl-licodiones were synthesized for comparison and the sole product of LMT-catalysed reaction was identified as 2′-O-methyl-licodione. A possible scheme for the last steps of echinatin biosynthesis is proposed. |
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Keywords: | Leguminosae cell culture cell free extract retrochalcone biosynthesis: enzyme echinatin licodione |
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