THE OCCURRENCE AND DETERMINATION OF δ-AMINOLEVULINIC ACID AND PORPHOBILINOGEN IN URINE

Abstract

A number of recent studies have shown that &aminolevulinic acid (SAL) and porphobilinogen (PBG) are early intermediates in the biosynthesis of porphyrins (l-4). Enzyme studies have also shown that PBG is formed by the condensation of 2 molecules of 6AL (5-7). The occurrence of 6AL in biological material has not been reported primarily because a method for its detection has not been available. In this paper, a sensitive calorimetric method for the quantitative determination of SAL is described. The analysis of 6AL in urine is also described. By means of this method, 6AL has been found in urine of a patient with acute porphyria (8) and also in normal urine. The determination of PBG is based on its reaction with p-dimethylaminobenzaldehyde (DMAB) (Ehrlich’s reagent) in acid solution to form a red compound. Determinations of PBG in urine are interfered with by urea, various pigments, and oxidizing and reducing agents (9). Various indole derivatives also give color tests with this reagent (10). Urobilinogen does not interfere at the acidities which are used (11). Because of the high concentration of PBG in the urine of patients with acute porphyria, Vahlquist (12) found that a semiquantitative determination could be made if the urine was diluted greatly, thus diminishing the effect of interfering substances. However, no method has been available for determining low or intermediate concentrations of PBG in urine. In this paper, methods are described for the quantitative determination of PBG in urine.