title: Erythrocyte porphobilinogen synthase (delta-aminolaevulinate dehydratase) activity: a reliable and quantitative indicator of lead exposure in humans.
abstract: We assessed optimal conditions for assay of porphobillinogen synthase (EC 4.2.1.24) activity in human blood containing abnormally high concentrations of lead. Zn2+and -SH, both required for complete activation of the enzyme, had additive effects. Using a modified method based on these studies, we found blood lead concentration to be strictly proportional to ln(activated/nonactivated) enzyme activity. One brand of commercially available "lead-free" tubes contained a substance that interfered with this relationship. In vitro studies, with the modified assay, showed ALAD to be activated by low concentrations but inactivated by high concentrations of Hg2+, Cd2+, and ethylenediaminetetraacetate. We fouund no genetically influenced differences among unexposed individuals when in(activated/nonactivated) enzyme activities were compared. The technique is suitable for use in screening for lead poisoning in humans.
mesh_terms: D002104:Cadmium / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D004912:Erythrocytes / Q000201:enzymology*; D005978:Glutathione / Q000494:pharmacology; D006801:Humans; D006836:Hydro-Lyases / Q000097:blood*; D007700:Kinetics; D007854:Lead / Q000097:blood / Q000494:pharmacology; D007855:Lead Poisoning / Q000175:diagnosis* / Q000201:enzymology*; D008628:Mercury / Q000494:pharmacology; D000623:Porphobilinogen Synthase / Q000097:blood*; D012964:Sodium / Q000494:pharmacology; D015032:Zinc / Q000494:pharmacology
chemical_list: D002104:Cadmium; D007854:Lead; D004492:Edetic Acid; D012964:Sodium; D006836:Hydro-Lyases; D000623:Porphobilinogen Synthase; D008628:Mercury; D005978:Glutathione; D015032:Zinc