LEAD TOXICITY AND THE ALA-DEHYDRATASE POLYMORPHISM

δ-氨基乙酰丙酸脱氢酶（ALA-D，EC 4.2.1.4）是一种锌酶， 金属酶，其铅的抑制作用是第一个也是最重要的 铅暴露的敏感指标， 与铅中毒的发病机制有关 该酶由两个等位基因ALA-D1和ALA-D2编码。 最近 我们实验室的证据表明 不太常见的等位基因ALA-D2的杂合子或纯合子， 血铅水平比类似暴露水平高10微克/毫升 ALA-D1等位基因纯合子的血铅患者 水平在20-50 μ g/dl的范围内。 这些结果表明 有一些基因易感的个体， 如果具有这种遗传基因的妇女的胎儿 易感性可能是先天性异常的高风险。 的 遗传易感性差异的生化基础 携带不同ALA-D同工酶的个体是未知的。 将采取分子方法来促进对 ALA-D基因多态性及其与血铅水平的关系 以人ALA-D全长cDNA为探针，用RT-PCR方法扩增了ALA-D的cDNA。 D1和ALA-D2将被克隆和测序，以确定精确的 多态性的本质。 ALA-D1和ALA-D2特异性 寡脱氧核苷酸探针将用于确认常见的 ALA-D 1-1和2-2个体中多态性的同一性。 或者ALA-D同工酶与铅的相互作用， 大量的人ALA-D 1-1和2-2将在 从E.大肠杆菌，它们的物理动力学特性将 与亲和纯化的红细胞同工酶进行比较。 所有 这些努力将被导向阐明 不同遗传易感性的生化基础 携带不同同工酶的个体血铅蓄积 的ALA-D。 此外，还将开发一种灵敏、快速的检测方法， 用单克隆抗体区分ALA-D1和2亚基 合成肽含有独特的ALA-D1和2 表位 这样的测试将是有价值的， 流行病学研究旨在确定遗传 易受影响的人，他们的健康风险会增加 如果在工作场所或环境中接触铅。

Delta-aminolevulinic acid dehydratase (ALA-D, EC 4.2.1.4) is a zinc metalloenzyme whose inhibition by lead is the first and most sensitive indicator of lead exposure and whose decreased activity has been clearly implicated in the pathogenesis of lead poisoning. The enzyme is encoded by two alleles, ALA-D1 and ALA-D2. Recent evidence from our laboratory indicates that individuals heterozygous or homozygous for the less common allele, ALA-D2, have blood lead levels 10 mu g/ml greater than similarly exposed individuals homozygous for the ALA-D1 allele who have blood lead levels in the range of 20-50 mu g/dl. These results suggest that there are genetically susceptible individuals who would be at an increased health risk if the fetuses of women with such a genetic susceptibility may be at higher risk for congenital anomalies. The biochemical basis for the differential genetic susceptibility of individuals carrying different isozymes of ALA-D is unknown. A molecular approach will be taken to facilitate studies of the ALA-D polymorphism and its association with blood lead levels. Using a full-length cDNA for human ALA-D as a probe, cDNAs for ALA- D1 and ALA-D2 will be cloned and sequenced to determine the precise nature of the polymorphism. ALA-D1 and ALA-D2-specific oligodeoxyribonucleotide probes will be used to confirm the common identity of the polymorphism in ALA-D 1-1 and 2-2 individuals. Alternatively the interaction of the ALA-D isozymes with lead, large quantities of human ALA-D 1-1 and 2-2 will be expressed in an purified from E. coli, and their physicokinetic properties will be compared with affinity purified isozymes from erythrocytes. All of these efforts will be directed toward elucidation of the biochemical basis for the differential genetic susceptibility to blood lead accumulation in individuals carrying different isozymes of ALA-D. In addition, a sensitive and rapid test will be developed to distinguish ALA-D 1 and 2 subunits using monoclonal antibodies produced to synthetic peptides containing unique ALA-D 1 and 2 epitopes. Such a test would be valuable for additional epidemiological studies aimed at identifying genetically susceptible individuals who would be at an increased health risk if exposed to lead in the workplace or environment.