Evidence for arylamine N-acetyltransferase in Hymenolepis nana.
N-acetyltransferase activities with p-aminobenzoic acid and 2-aminofluorene were determined in Hymenolepis nana, a cestode found in the intestine of the Sprague-Dawley rats. The N-acetyltransferase activity was determined using an acetyl CoA recycling assay and high pressure liquid chromatography. The N-acetyltransferase activities from a number of Hymenolepis nana whole tissue homogenizations were found to be 2.83 +/- 0.31 nmole/min/mg for 2-aminofluorene and 2.07 +/- 0.24 nmole/min/mg for p-aminobenzoic acid. The apparent Km and Vmax were 1.06 +/- 0.38 mM and 8.92 +/- 1.46 nmol/min/mg for 2-aminofluorene, and 2.16 +/- 0.19 mM and 12.68 +/- 2.26 nmol/min/mg for p-aminobenzoic acid. The optimal pH value for the enzyme activity was pH 8.0 for both substrates tested. The optimal temperature for enzyme activity was 37 degrees C for both substrates. The N-acetyltransferase activity was inhibited by iodacetamide. At 0.25 mM iodacetamide the activity was reduced 50% and 1.0 mM iodacetamide inhibited activity more than 90%. Among a series of divalent cations and salts, Fe2+, Ca2+ and Zn2+ were demonstrated to be the most potent inhibi-tors. Among the protease inhibitors, only ethylenediaminetetraacetic acid significantly protected N-acetyltransferase. Iodoacetate, in contrast to other agents, markedly inhibited N-acetyltransferase activity. This is the first demonstration of acetyl CoA:arylamine N-acetyltransferase activity in a cestode and extends the number of phyla in which this activity has been found.
Chung
J G
JG
Department of Medicine, China Medical College, Taichung, Taiwan, Republic of China.
Kuo
H M
HM
Wu
L T
LT
Lai
J M
JM
Lee
J H
JH
Hung
C F
CF
D000818:Animals; D001191:Arylamine N-Acetyltransferase / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D006926:Hymenolepis / Q000201:enzymology*; D007460:Iodoacetamide / Q000494:pharmacology; D007700:Kinetics; D011480:Protease Inhibitors / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013696:Temperature
D011480:Protease Inhibitors; D001191:Arylamine N-Acetyltransferase; D007460:Iodoacetamide