LEAD TOXICITY AND THE ALA-DEHYDRATASE POLYMORPHISM

-氨基乙酰丙酸脱水酶(ALA-D，EC 4.2.1.4)是一种锌 铅抑制作用最强的金属酶 铅暴露及其活性降低的敏感指标 已明确与铅中毒的发病机制有关。 该酶由ALA-D1和ALA-D2两个等位基因编码。近期 我们实验室的证据表明，个人 较少见的等位基因ALA-D2的杂合子或纯合子有 血铅水平比同等暴露水平高10微克/毫升 有血铅的ALA-D1等位基因纯合子个体 水平在20-50微克/分升之间。这些结果表明， 有一些遗传易感的个体会在一个 如果具有这种基因的女性的胎儿会增加健康风险 易感性可能是先天异常的较高风险。这个 血吸虫病不同遗传易感性的生化基础 携带不同ALA-D同工酶的个体尚不清楚。 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的全长cDNA为探针，以ALA-D的cDNAs为探针，建立了人ALA-D的全长DNA序列。 D1和ala-d2将被克隆和测序，以确定准确的 多态的性质。ALA-D1和ALA-D2特异性 将使用寡脱氧核苷酸探针来确认常见的 ALA-D 1-1和2-2个体的多态同源性。 或者，ALA-D同工酶与铅的相互作用， 大量人类ALA-D 1-1和2-2将在 从大肠杆菌中提纯的一株，它们的物理动力学性质将 与红细胞亲和纯化同工酶进行比较。全 这些努力的目的将是阐明 甲型肝炎不同遗传易感性的生化基础 不同同工酶携带者的血铅蓄积 阿拉巴马州的。 此外，还将开发一种敏感和快速的检测方法，以 用单抗区分ALA-D_1和ALA-D_2亚基 合成含有唯一丙氨酸D_1和丙氨酸D_2的合成肽 表位。这样的测试将对其他 旨在识别基因的流行病学研究 健康风险增加的易感人群 如果在工作场所或环境中暴露于铅中。

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.