INVOLVEMENT OF ARGININE RESIDUES IN THE CATALYTIC ACTIVITY OF CATECHOL-O-METHYLTRANSFERASE

1. 1. Phenylglyoxal, a specific chemical modifier of arginine residues, rapidly inactivated brain and liver catechol-O-methyltransferase (COMT) of rat. 2. 2. The inactivation was first order dependent, and the rate was calculated as 0.71 min-7 and 0.67 min-1 at pH 7.8 and 23°C for the brain and liver enzyme respectively. 3. 3. The presence of the substrate S-adenosyl-methionine during the preincubation of COMT with the phenyl-glyoxal markedly reduced the rate of inactivation. 4. 4. Three other dicarbonyl compounds 2,4-pentanedione, 2,3-butanedione and 1,2-cyclohexanedione also inactivated the enzyme. 5. 5. The results suggest that arginine residues play an important role in the catalytic activity of rat brain and liver COMT. © 1979.