Monomorphic and polymorphic isozymes of arylamine N-acetyltransferases in hamster liver: purification of the isozymes and genetic basis of N-acetylation polymorphism.
Two forms of cytosolic acetyltransferases, AT-I and AT-II, have been purified from hamster livers, and a comparison made of their chemical and catalytic properties and genetically expressed difference. Homogeneous AT-I and AT-II were 31 and 30 kd respectively on SDS-PAGE and catalyzed efficiently various N- and O-acetylations in their reconstitution systems. AT-I used both acetyl CoA and arylhydroxamic acids as acetyl donors, while AT-II did not utilize arylhydroxamic acids as acetyl donors. In the reconstitution system, purified AT-I, but not AT-II, catalyzed acetyl CoA-dependent O-acetylation of 2-N-hydroxyamino-6-methyldipyrido[1,2-alpha:3', 2'-d]imidazole (N-OH-Glu-P-1) and arylhydroxamic acid-dependent N-acetylation of 4-aminoazobenzene (AAB). On the other hand purified AT-II showed high activities of acetyl CoA-dependent N-acetylation of 2-aminofluorene (AF) and p-aminobenzoic acid (PABA). Polyclonal antibodies raised against AT-I inhibited cytosolic acetylations of N-OH-Glu-P-1 and AAB, and to a lesser extent of AF, while PABA N-acetylation was only marginally inhibited. Using Western blots, both AT-I and AT-II were recognized by the antibodies. AT-I was detectable in all the livers examined, and the content did not differ among the individuals (monomorphic distribution). In contrast, AT-II was distributed polymorphically, and the trimodal distribution of AT-II (high, intermediate and low) was correlated with the phenotype identified by cytosolic N-acetylations of AF and PABA (rapid, intermediate and slow). In addition, cross-mating experiments with intra- and inter-phenotype animals confirmed that hepatic AT-II isozyme is inherited by a Mendelian co-dominant trait. These results indicate that the polymorphic appearance of an acetyltransferase, AT-II, is responsible for the N-acetylation polymorphism in individual hamsters.
Ozawa
S
S
Department of Pharmacology, School of Medicine, Keio University, Tokyo, Japan.
Abu-Zeid
M
M
Kawakubo
Y
Y
Toyama
S
S
Yamazoe
Y
Y
Kato
R
R
D010129:4-Aminobenzoic Acid; D000105:Acetyl Coenzyme A / Q000494:pharmacology; D000107:Acetylation; D000818:Animals; D001191:Arylamine N-Acetyltransferase / Q000032:analysis / Q000235:genetics* / Q000302:isolation & purification; D015153:Blotting, Western; D002846:Chromatography, Affinity; D002851:Chromatography, High Pressure Liquid; D006224:Cricetinae; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005449:Fluorenes / Q000378:metabolism; D007093:Imidazoles / Q000378:metabolism; D007527:Isoenzymes / Q000302:isolation & purification; D008099:Liver / Q000201:enzymology*; D008297:Male; D009153:Mutagens; D011110:Polymorphism, Genetic; D010128:p-Aminoazobenzene / Q000378:metabolism
D005449:Fluorenes; D007093:Imidazoles; D007527:Isoenzymes; D009153:Mutagens; C012177:2-aminofluorene; D010128:p-Aminoazobenzene; D000105:Acetyl Coenzyme A; C023786:2-hydroxyamino-6-methyldipyrido(1,2-a-3',2'-d)imidazole; D001191:Arylamine N-Acetyltransferase; D010129:4-Aminobenzoic Acid