N-acetylation of the heterocyclic amine batracylin by human liver.
Batracylin (8-aminoisoindolo[1,2-b]quinazolin-12(10 H)-one; BAT) is a heterocyclic amine that exhibits antitumor activity in a number of in vivo and in vitro models. The acetyl product has been implicated in BAT toxicity in animals, cells, and bacteria. The ability of human N-acetyltransferase (NAT) to form this product was investigated. Nine human liver samples were analyzed for NAT1 and NAT2 genotypes. Seven of the samples possessed at least one NAT1*4 allele. Three samples contained one or more NAT2*4 allele and were classified as rapid acetylators. The remaining six had two alleles associated with the slow phenotype. NAT activities were evaluated with BAT, sulfamethazine (SMZ), a preferential substrate for human NAT2, and p-aminobenzoic acid, a substrate for NAT1. BAT activities in the nine donor samples ranged from 14.9 to 0.56 nmol/min/mg. The mean apparent K(m) values in rapid acetylators for BAT, SMZ, and p-aminobenzoic acid were 6.59 +/- 3.21, 278 +/- 69.4, and 31.2 +/- 12.5 microM, respectively. The apparent K(m) values for slow acetylators did not differ from the rapid acetylator phenotype. However, a significant difference in the apparent V(max) for BAT and SMZ was observed between rapid and slow acetylators. Comparing the apparent intrinsic clearance (V(max)/K(m)) for BAT and SMZ, a significant correlation (r(2) = 0.97, p <.001) was observed. These data demonstrate that BAT N-acetylation is similar to SMZ, and suggests that BAT is a preferential substrate for human NAT2. Thus, rapid acetylators would be more likely to develop toxicity when exposed to this drug.
Stevens
G J
GJ
Department of Pharmacology and Toxicology, University of Arizona, Tucson, Arizona 85721, USA.
Payton
M
M
Sim
E
E
McQueen
C A
CA
D010129:4-Aminobenzoic Acid / Q000378:metabolism; D000107:Acetylation; D000328:Adult; D000368:Aged; D000970:Antineoplastic Agents / Q000378:metabolism*; D001191:Arylamine N-Acetyltransferase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D002675:Child, Preschool; D003001:Cloning, Molecular; D003600:Cytosol / Q000378:metabolism; D017931:DNA Primers; D005260:Female; D005838:Genotype; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D011799:Quinazolines / Q000378:metabolism*; D013418:Sulfamethazine / Q000378:metabolism
D000970:Antineoplastic Agents; D017931:DNA Primers; D011799:Quinazolines; D013418:Sulfamethazine; C057924:batracylin; D001191:Arylamine N-Acetyltransferase; D010129:4-Aminobenzoic Acid