PROPERTIES OF AN ARYLALKYLAMINE N-ACETYLTRANSFERASE FROM THE NEMATODE, ASCARIDIA-GALLI

1. An arylalkylamine N-acetyltransferase (NAT) of the parasitic nemato de, Ascaridia galli was studied using either [C-14]serotonin (5-HT) or [C-14]octopamine (OA) as substrates and with acetyl-CoA as the donor of the acetate group. 2. The NAT activity towards 5-HT and OA co-elute d from a size-exclusion column and appeared to have an M(r) of around 30,000. The enzyme had apparent K(m) values of 540 +/- 100 muM (+/- SE M) and 33 +/- 4 muM (+/- SEM) for 5-HT and octopamine, respectively, w hen assayed in the presence of 1 mM acetyl-CoA. 3. High levels of NAT were found in the gonads of male and female worms and the muscle/body wall. 4. N-acetylation was strongly inhibited by Cu2+ but not by other divalent metal ions and the effect of a number of compounds including biogenic amines, formamidines, hydrazines, and beta-carbolines on the arylalkylamine N-acetyltransferase activity was studied.