Characterization of the arylalkylamine N-acetyltransferase in Onchocerca volvulus.
The characteristics and kinetic properties of an arylalkylamine N-acetyltransferase were studied in partially purified preparations of the human filarial parasite Onchocerca volvulus. The enzyme, which had a relative molecular mass (M(r)) of 37-38 kDa, catalyzed the acetylation of arylalkylamines but did not accept arylamines or polyamines as substrates. The optimal pH for enzyme activity was found to be 8.5 in TRIS-HCI. The apparent Michaelis constant (K(m)) and maximum velocity (Vmax) determined from Lineweaver-Burk plots for tryptamine were 1.8 microM and 29 nmol min-1 mg protein-1, respectively. Except for the catecholamines, the other arylalkylamines such as 5-hydroxytryptamine (5-HT), tyramine, and octopamine similarly exhibited high affinities and reaction rates. Whereas the enzyme is inhibited by metals and p-chloro-mercuribenzoate, it is inactivated neither by amethopterin nor by cystamine and is thereby distinguished from the mammalian arylamine N-acetyltransferase. Like other N-acetyltransferases whose function is the regulation of intracellular amine levels, the enzyme may have a role in the inactivation of excess biogenic amine in this parasite.
Aisien
S O
SO
Department of Zoology, University of Benin, Nigeria.
Hellmund
C
C
Walter
R D
RD
D000818:Animals; D001191:Arylamine N-Acetyltransferase / Q000302:isolation & purification / Q000378:metabolism*; D002395:Catecholamines / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008322:Mammals; D017181:Onchocerca volvulus / Q000201:enzymology* / Q000302:isolation & purification; D009855:Onchocerciasis / Q000469:parasitology; D013379:Substrate Specificity
D002395:Catecholamines; D001191:Arylamine N-Acetyltransferase