title: Borate and molybdate inhibition of catechol estrogen and pyrocatechol methylation by catechol-O-methyltransferase.
abstract: The possibility that boron and molybdenum anions can influence sex steroid metabolism by forming complexes with catechol estrogens has been studied in vitro. The formation of 2-methoxyestrone (2-OHE1 2-Me) from 2-hydroxyestrone (2-OHE1) by catechol-O-methyltransferase (COMT) was followed by measuring the transfer of the radiolabeled methyl group from S-adenosylmethionine. In the presence of both sodium tetraborate and sodium molybdate using a phosphate buffer medium, the formation of 2-OHE1 2-Me decreased as the anion:2-OHE1 molar ratio was increased. However, the reverse effect was observed when using a tris buffer medium and further investigation showed that phosphate and sulphate also enhanced COMT activity in a tris buffer medium. Boric acid affinity medium, used as a substitute for borate salt, also showed a negative relationship with enzyme activity in a phosphate buffer medium, and inhibition of methylation was more marked than with the free anion. Erythrocytes contain appreciable amounts of COMT, which is mostly responsible for the rapid O-methylation of catechol estrogens in blood. The methylation of a simple catechol compound, 1,2-dihydroxybenzene (pyrocatechol) was therefore studied using rat red blood cell lysates. Methylation was inhibited in a concentration-related manner by borate, as found in the studies of 2-OHE1. It is possible that high dietary intakes of boron or molybdenum could regulate the rate of catabolism, or even the metabolic fate of the major estrogens.
authors.affiliation: Division of Biochemical Sciences, Rowett Research Institute, Bucksburn, Aberdeen, U.K.
authors.forename: J H
authors.initials: JH
authors.lastname: Beattie
authors.forename: E
authors.initials: E
authors.lastname: Weersink
mesh_terms: D000818:Animals; D001881:Borates / Q000494:pharmacology*; D002394:Catechol O-Methyltransferase / Q000097:blood; D065098:Catechol O-Methyltransferase Inhibitors; D002396:Catechols / Q000378:metabolism*; D004912:Erythrocytes / Q000201:enzymology; D002393:Estrogens, Catechol / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008745:Methylation; D008982:Molybdenum / Q000494:pharmacology*; D051381:Rats
chemical_list: D001881:Borates; D065098:Catechol O-Methyltransferase Inhibitors; D002396:Catechols; D002393:Estrogens, Catechol; D008982:Molybdenum; C010634:sodium borate; C024687:sodium molybdate(VI); D002394:Catechol O-Methyltransferase; C034221:catechol