Interferences in the δ-Aminolevulinic Acid Dehydratase (ALA-D) Assay

Abstract

A systematic study of the effect of procedural variables on the ALA-D assay has been carried out. Because of metal content in vacutainers, artifactual results are obtained on blood samples drawn by this method and the method of choice is the use of plastic syringes and tubes. The use of isopropyl alcohol as a skin sterilizing agent, although it gives measurable blood alcohol readings, does not affect the ALA-D assay. The handling of the whole blood has been investigated and the two methods of hemolysis compared. Trichloroacetic acid, a reagent used in the final assay of porphobilinogen, has been found to be a serious interference in the method, making it essential for this reagent to be kept in a securely sealed container. The deterioration of the trichloroacetic acid--mercuric chloride reagent is also a potential procedural problem that must be considered.

Kinetic parameters of the inhibition of red blood cell aminolevulinic acid dehydratase by triethyl lead and its reversal by dithiothreitol and zinc

“…This finding is in agreement with the work of others using inorganic lead compounds (10,11). The value of the apparent Ki (5.2 x lo4 M) determined for 3EL is slightly less than two orders of magnitude than that reported for inorganic lead (Ki + 1.7 x lo4 M) (12) and may account for the greater toxicity shown by the alkyl lead compounds (7).…”

Evaluation of the relationship between chemical and biological monitoring of low‐level lead poisoning

“…Nevertheless, despite this shallow curve, the shift of the pH of maximum enzyme activity to more acidic values is un- mistakeable. The pH-activity curves for the other dosing periods (7,21, and 35 days) show similar features except that the activities are progressively lower, reflecting the growing maturity of the animals. Complete activity data, including the restored (dithiothreitol) activity values are shown in Table 2.…”

Direct Assay of δ-Aminolevulinic Acid Dehydratase in Heme Biosynthesis for the Detection of Porphyrias by Tandem Mass Spectrometry

“…Current assays for ALAD deficiency are, for the most part, based on a method developed by Mauzerall and Granick in 1956 . This technique involves reacting the enzymatic product with p -dimethylaminobenzaldehyde, or Erlich’s reagent, to create a compound detectable by colorimetry or fluorimetry. − A common alternative is a coupled-enzyme assay, , wherein porphobilinogen is carried further down the biosynthetic pathway to produce hydroxymethylbilane, which spontaneously cyclizes to uroporphyrinogen I, which is then oxidized and detected as uroporphyrin I by fluorimetry. None of the current methods detect porphobilinogen directly, putting them at a clear disadvantage compared to a method that does.…”