Effects of ethoxyquin on hepatic microsomal enzymes

PROCEEDINGS OF THE BIOCHEMICAL SOCIETY achieved with sodium deoxycholate (3g/1) in 0.2M-Na2HPO4 adjusted to pH6.5 with 0.2M-KH2PO4.The solubilized enzyme, in the presence of sodium deoxycholate, has a pH optimum of 7.9, which approaches that of the cytoplasmic catechol 0- methyltransferase.Under our experimental conditions tyramine, a monohydroxy amine, does not serve as a substrate for the microsomal preparations.The optimal sub- strate concentrations of L-adrenaline and L-nor- adrenaline were found to be similar for both enzymes.The total activities of the cytoplasmic and micro- somal catechol O-methyltransferases in the livers of normal rats were investigated.The relative ratios of specific activities of the two enzymes were found to increase in rats subjected to isolation and in those treated orally with phenobarbitone (23 mg/day).