Slow acetylation in mice is caused by a labile and catalytically impaired mutant N-acetyltransferase (NAT2 9).
Slow acetylation in mice is caused by a labile and catalytically impaired mutant N-acetyltransferase (NAT2 9).
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发表时间：
1995-12
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通讯作者：
J. H. de león;K. Martell;K. P. Vatsis;W. Weber
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作者：
J. H. de león;K. Martell;K. P. Vatsis;W. Weber
三个N-乙酰基转移酶基因（NAT*）在近交系小鼠的父母和同类检测。用NAT 2特异性（对氨基苯甲酸）和NAT 2选择性（2-氨基芴）底物对NAT 2 * 和肝细胞溶质N-乙酰化活性测定进行直接测序，已确定乙酰化同源A.B6和B6.A小鼠分别与其起源的亲本B6（“野生型”;快速乙酰化）和A（突变型;缓慢乙酰化）小鼠在基因型和表型上相同。对氨基苯甲酸的表观KM和热灭活率测定与肝胞质溶胶从突变体（A和B6.A）小鼠是3倍，一个数量级高于相应的值与肝胞质溶胶从野生型（B6和A.B6）菌株。无论动物的NAT 2 * 基因型或表型如何，北方印迹和免疫印迹显示肝脏NAT 2 mRNA和蛋白条带大小和强度相等。突变A和B6.A小鼠的肝胞液在37 ℃下孵育6小时导致对氨基苯甲酸酯N-乙酰化活性的实际停止，而免疫反应性NAT 2的稳态水平保持不变。结果表明，来自慢乙酰化小鼠的突变型NAT 2 * 中的氨基酸变化（N99 I）不会阻碍肝NAT 2蛋白的合成，而是导致产生构象修饰的NAT 2分子，其抵抗组织蛋白酶的降解，但不稳定且催化受损。
Three N-acetyltransferase genes (NAT*) were detected in inbred parental and congenic mice. Direct sequencing of NAT2* and liver cytosolic N-acetylation activity determinations with NAT2-specific (p-aminobenzoic acid) and NAT2-selective (2-aminofluorene) substrates have established that the acetylator congenic A.B6 and B6.A mice are genotypically and phenotypically identical to the parental B6 ("wild-type"; rapid acetylator) and A (mutant; slow acetylator) mice, respectively, from which they originated. The apparent KM for p-aminobenzoic acid and thermal inactivation rates determined with liver cytosol from the mutant (A and B6.A) mice were 3-fold and one order of magnitude higher than the corresponding values with liver cytosol from the wild-type (B6 and A.B6) strains. Northern blotting and immunoblotting revealed hepatic NAT2 mRNA and protein bands of equal size and intensity, regardless of the NAT2* genotype or phenotype of the animals. Incubation of liver cytosol from mutant A and B6.A mice at 37 degrees C for 6 hr resulted in virtual cessation of p-aminobenzoate N-acetylation activity, whereas the steady-state level of immunoreactive NAT2 remained unchanged. The results indicate that the amino acid change (N99I) in mutant NAT2* from slow acetylator mice does not hinder the synthesis of hepatic NAT2 protein, but, rather, leads to production of a conformationally modified NAT2 molecule that resists degradation by tissue proteases but is labile and catalytically impaired.