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.

Agency
National Institute of Health (NIH)
Institute
National Institute of Environmental Health Sciences (NIEHS)
Type
Research Project (R01)
Project #
5R01ES005046-03
Application #
3253277
Study Section
Toxicology Subcommittee 2 (TOX)
Project Start
1989-05-01
Project End
1992-04-30
Budget Start
1991-05-01
Budget End
1992-04-30
Support Year
3
Fiscal Year
1991
Total Cost
Indirect Cost
Name
Mount Sinai School of Medicine
Department
Type
Schools of Medicine
DUNS #
City
New York
State
NY
Country
United States
Zip Code
10029
Fleming, D E; Chettle, D R; Wetmur, J G et al. (1998) Effect of the delta-aminolevulinate dehydratase polymorphism on the accumulation of lead in bone and blood in lead smelter workers. Environ Res 77:49-61
Bergdahl, I A; Grubb, A; Schutz, A et al. (1997) Lead binding to delta-aminolevulinic acid dehydratase (ALAD) in human erythrocytes. Pharmacol Toxicol 81:153-8
Bergdahl, I A; Gerhardsson, L; Schutz, A et al. (1997) Delta-aminolevulinic acid dehydratase polymorphism: influence on lead levels and kidney function in humans. Arch Environ Health 52:91-6
Todd, A C; Wetmur, J G; Moline, J M et al. (1996) Unraveling the chronic toxicity of lead: an essential priority for environmental health. Environ Health Perspect 104 Suppl 1:141-6
Wetmur, J G (1994) Influence of the common human delta-aminolevulinate dehydratase polymorphism on lead body burden. Environ Health Perspect 102 Suppl 3:215-9
Kaya, A H; Plewinska, M; Wong, D M et al. (1994) Human delta-aminolevulinate dehydratase (ALAD) gene: structure and alternative splicing of the erythroid and housekeeping mRNAs. Genomics 19:242-8
Wetmur, J G; Lehnert, G; Desnick, R J (1991) The delta-aminolevulinate dehydratase polymorphism: higher blood lead levels in lead workers and environmentally exposed children with the 1-2 and 2-2 isozymes. Environ Res 56:109-19
Plewinska, M; Thunell, S; Holmberg, L et al. (1991) delta-Aminolevulinate dehydratase deficient porphyria: identification of the molecular lesions in a severely affected homozygote. Am J Hum Genet 49:167-74
Wetmur, J G (1991) DNA probes: applications of the principles of nucleic acid hybridization. Crit Rev Biochem Mol Biol 26:227-59
Wetmur, J G; Kaya, A H; Plewinska, M et al. (1991) Molecular characterization of the human delta-aminolevulinate dehydratase 2 (ALAD2) allele: implications for molecular screening of individuals for genetic susceptibility to lead poisoning. Am J Hum Genet 49:757-63

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