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Updated: Jul 10, 2026

In Vitro Assay to Measure Phosphatidylethanolamine Methyltransferase Activity
Published on: January 5, 2016
2-hydroxyethynyloestradiol as a substrate for catechol-O-methyltransferase--implications in the metabolism of
Abstract:
Highly purified pig catechol-O-methyltransferase catalyses the methylation of 2-hydroxyethynyloestradiol (KM - 11.0 microM, Vmax = 521.2 mU/mg protein, Vmax/KM = 47.4) more efficiently than that of 2-hydroxyoestradiol (KM = 68.5 microM, Vmax = 1056.2 mU/mg protein, Vmax/Km = 15.4), 2-hydroxyoestrone (KM = 38.0 microM, Vmax = 795.0 mU/mg protein, Vmax/KM = 20.9) or 4-hydroxyoestrone (KM = 12.8 microM, Vmax = 159.7, Vmax/KM = 12.5). This efficient methylation of the principal metabolite of ethynyloestradiol substantiates the implications of the studies of Bolt et al.[1] that O-methylation is a major route of ethynyloestradiol metabolism. Furthermore, this also implies that catechol-O-methyltransferase in involved in the protection, by S-adenoysylmethionine, against the impairment of bile secretion by ethynyloestradiol, observed in female rats [2].
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