Studies on the biosynthesis of blood pigments. 3. Haem and porphyrin formation from δ-aminolaevulic acid and from porphobilinogen in haemolysed chicken erythrocytes

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Abstract
The quantitative and qualitative equivalence of haem and porphyrin formation from ALA and PBG in the fowl haemolysate preparation is demonstrated. At low substrate concentrations, only haem and protoporphyrin were formed, but, with higher substrate concentrations, porphyrins with more than two carboxyl side-chains also accumulated. The main porphyrins other than protoporphyrin were coproporphyrin HI uroporphyrin HI and a new porphyrin which was called pseudouroporphyrin. The conversion of ALA and PBG into porphyrins was very efficient and approached 90% under certain conditions. Haem synthesis was relatively inefficient in this preparation but was much increased, with a corresponding decrease of free protoporphyrin, by the addition of 10-3 ferrous sulfate. Supernatant fractions obtained from the haemolysate after high-speed centrifuging converted ALA and PBG into "coproporphyrins" and "uroporphyrins" only no significant amounts of protoporphyrin or haem being observed. Some comparisons of these preparations with similar preparations from duck cells, and also with homogenized preparations, are described. Addition of l0-4 [image] lead acetate resulted in an almost total inhibition of haem synthesis from glycine, scarcely any inhibition of haem and porphyrin formation from PBG, and a considerable inhibition of porphyrin formation from ALA. It is suggested that, if lead specifically inhibits haem synthesis in vivo, the step most sensitive to this reagent must be among the early steps leading to the synthesis of ALA.