Trepanier L A, Cribb A E, Spielberg S P, Ray K
Department of Pharmacology, Cornell University, College of Veterinary Medicine, Ithaca, NY, USA.
Pharmacogenetics. 1998 Apr;8(2):169-79. doi: 10.1097/00008571-199804000-00009.
The purpose of this study was to determine the molecular basis for a relative deficiency in the cat of cytosolic arylamine N-acetyltransferase (NAT), an enzyme family that is important in the metabolism of xenobiotics and that normally consists of at least two related enzymes, NAT1 and NAT2. N-acetyltransferase in feline liver showed high affinity (mean Km = 2.1 microM) for p-aminobenzoic acid, an NAT1 selective substrate in humans and rabbits, but showed a very poor affinity (mean Km > 10 mM) for sulfamethazine, an NAT2 selective substrate in humans and rabbits. Immunoreactive N-acetyltransferase was detected in feline liver, bladder and colon using an NAT1-specific antipeptide antibody, but was not detected in any tissues using an NAT2-specific antibody. Southern blot analysis of genomic DNA demonstrated a single band in domestic cats using each of six restriction digests; single bands were also found on Southern blot analysis of six wild felids. The deduced amino acid sequence of the central portion of feline N-acetyltransferase, obtained by polymerase chain reaction amplification in both domestic cats and seven wild felids (lion, tiger, lynx, snow leopard, bobcat, Asian leopard cat and cheetah), contained three residues, Phe125, Arg127, and Tyr129, which determine NAT1-like substrate specificity in humans. These results support the conclusion that cytosolic arylamine N-acetylation activity is low in the cat because of the presence of a single N-acetyltransferase that has substrate specificity, immunogenicity and sequence characteristics similar to human NAT1, and that the unusual presence of only a single N-acetyltransferase gene appears to be a family wide trait shared by other felids.
本研究的目的是确定猫体内胞质芳胺N - 乙酰转移酶（NAT）相对缺乏的分子基础，该酶家族在异生物代谢中起重要作用，通常由至少两种相关酶NAT1和NAT2组成。猫肝脏中的N - 乙酰转移酶对对氨基苯甲酸表现出高亲和力（平均Km = 2.1 microM），对氨基苯甲酸是人和兔体内NAT1的选择性底物，但对磺胺二甲嘧啶表现出非常低的亲和力（平均Km > 10 mM），磺胺二甲嘧啶是人和兔体内NAT2的选择性底物。使用NAT1特异性抗肽抗体在猫的肝脏、膀胱和结肠中检测到免疫反应性N - 乙酰转移酶，但使用NAT2特异性抗体在任何组织中均未检测到。基因组DNA的Southern印迹分析显示，在六次限制性酶切中的每次酶切下，家猫中均出现一条带；在对六种野生猫科动物的Southern印迹分析中也发现了单条带。通过聚合酶链反应扩增在当家猫和七种野生猫科动物（狮子、老虎、猞猁、雪豹、山猫、亚洲豹猫和猎豹）中获得的猫N - 乙酰转移酶中央部分的推导氨基酸序列包含三个残基，即Phe125、Arg127和Tyr129，它们决定了人类中NAT1样底物特异性。这些结果支持以下结论：由于存在单一的具有与人类NAT1相似的底物特异性、免疫原性和序列特征的N - 乙酰转移酶，猫体内胞质芳胺N - 乙酰化活性较低，并且仅存在单一N - 乙酰转移酶基因这一不寻常现象似乎是其他猫科动物共有的家族特征。
