Kinetic and electrophoretic properties of catechol O-methyltransferases (EC 188.8.131.52) from brain and liver were studied. The enzyme of either rat or human tissues exhibited a single molecular form when subjected to electrophoresis at pH7.9. At pH9 a second, apparently oxidized, form was detected. Isoelectric-focusing experiments also indicated only one enzyme form, which was identical from extracts of brain and liver of each species (pI = 5.2 for rat, 5.5 for human). Similarities between brain and liver catechol O-methyltransferase of a given species were also demonstrated by kinetic parameters, meta/para ratios of products, and inhibitor potencies. Human catechol O-methyltransferase exhibited lower Km values than did the rat enzyme for S-adenosyl-L-methionine, dopamine and dihydroxybenzoic acid. Adrenochrome inhibited both rat and human enzyme. It was concluded (1) that only a single enzyme form could be demonstrated in the physiological pH region; (2) that catechol O-methyltransferase of brain could not be distinguished from the liver enzyme of the same species; and (3) that species differences exist between the enzymes of rat and human tissues.
Research Article|February 01 1975
Properties of catechol O-methyltransferases from brain and liver of rat and human
H L White;
Biochem J (1975) 145 (2): 135-143.
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H L White, J C Wu; Properties of catechol O-methyltransferases from brain and liver of rat and human. Biochem J 1 February 1975; 145 (2): 135–143. doi: https://doi.org/10.1042/bj1450135
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