Subcellular site of porphyrin biosynthesis in nucleated erythrocytes

¹ Department of Physiological Chemistry, Wayne State University School of Medicine, Detroit, Michigan

The activity of hemolysates, prepared by several different methods from nucleated (chicken) erythrocytes, and of their subcellular fractions in forming porphyrins from glycine plus acetate or succinate or from -aminolevulinic acid (ALA) was studied. In general, hemolysates were less active than intact cells in porphyrin biosynthesis from glycine and acetate but were more active with ALA as the substrate. The supernatant fraction formed coproporphyrin from ALA but not from glycine and acetate. Protoporphyrin was not formed from either precursor by the supernatant fraction. The particulate fraction alone was devoid of porphyrin-forming activity, and also of ALA- and porphobilinogen- (PBG) forming activity. The combined particulate-supernatant fractions, however, synthesized both copro- and protoporphyrins from either glycine and acetate or ALA, but of course more from the latter. Dialysis or heating to 60 C destroyed the activity of the supernatant. These results indicate that "compartmentation" of porphyrin biosynthesis occurs in the nucleated erythrocyte much as in the liver cell, the step from ALA to coproporphyrinogen being carried out in the soluble, "nonparticulate" cellular fraction and the remaining steps in the "particulate" fraction.

Key Words: protoporphyrin • subcellular fractions • hemolysates • coproporphyrin

Submitted on July 15, 1964