Initial stages in the biosynthesis of porphyrins. 1. The formation of δ-aminolaevulic acid by particles obtained from chicken erythrocytes

Abstract

Particles have been obtained, from lysates of erythrocytes of anemic chickens, which catalyze a net synthesis of [delta]-aminolevulic acid from glycine and succinate or [alpha]-oxoglutarate. [delta]-Aminolevulic acid was not further metabolized by these particles. Preparations from non-anemic chickens had little or no activity. Synthesis of [delta]-aminolevulic acid required the addition of glycine, succinate or [alpha]-oxoglutarate and the presence of O2, and was increased by the addition of pyridoxal phosphate, coenzyme A, phosphate and magnesium chloride. Inhibition of synthesis of [delta]-aminolevulic acid was produced by addition of cyanide, iodoacetamide and p-chloromercuribenzoate. Ethylenediaminetetra-acetic acid showed a marked stimulating action. A number of other substances such as sodium azide, 2,4-dinitrophenol and sodium fluoride had no significant effect. The pH optimum was near 7.2, when phosphate buffer was used. Replacement of phosphate by borate, barbitone or 2-amino-2-hydroxymethylpropane-l,3-diol (tris) buffer reduced the amount of [delta]-aminolevulic acid formed. L-Penicillamine, but not D-Penicillamlne, was strongly inhibitory. It is suggested that this inhibition is caused by interaction with pyridoxal phosphate. No [delta]-aminolevulic acid was formed when succinate or [alpha]-oxoglutarate was replaced by synthetic succinyl-coenzyme A. It is suggested that this is the result of permeability barriers. The decarboxylation of glycine by the particles was greatly increased by addition of [alpha]-oxoglutarate.