ENZYMES OF PORPHYRIN SYNTHESIS IN RED BLOOD CELLS

Analysis of porphyrins and enzymes in porphyrin synthesis in Taenia solium cysticercus from man and pig

Porphyrins and activities of heme biosynthetic enzymes in Taenia solium cysticerci from porcine and human hosts, were examined in order to clarify the possible step where heme synthesis is interrupted. Porphyrins in the vesicular fluid of the parasite were predominantly coproporphyrin, followed by penta-carboxylated porphyrin, which together accounted for 90% of the accumulated porphyrins. Coproporphyrin and penta-carboxylated porphyrin were both type I and III isomers. Small amounts of protoporphyrin and uroporphyrin, and trace amounts of tri-, hexa- and hepta-carboxylated porphyrins were also detected. Fluorescence and phosphorescence spectra and lifetime studies revealed that at least 75% of the porphyrins were bound to metal, probably Zn, while the rest was free. Reverse phase high performance liquid chromatography monitored at an excitation wavelength of 417 nm and at an emission wavelength of 585 nm demonstrated that approximately 90% of these porphyrins were Zn-coproporphyrin. A fluorescence excitation peak at 283 nm with an emission peak at 585 nm and 625 nm indicated that some of the porphyrins were associated with proteins in the vesicular fluid of the parasite. Low levels of delta-aminolevulinic acid dehydratase, porphobilinogen deaminase and uroporphyrinogen decarboxylase activities, and heme concentrations were found in the extract of the parasite walls and scolex, but not in the vesicular fluid. The porphyrin accumulation pattern in this parasite can best be explained by postulating a deficiency of coproporphyrinogen oxidase activity, similar to that in human patients with hereditary coproporphyria. A parasite dissected from a human host was considerably less porphyric than those from pigs, but the pattern of accumulated porphyrins was quite similar in both. In view of their porphyrin contents, T. solium cysticerci could be light sensitive.

The erythrocyte protoporphyrin in chronic renal failure

The erythrocyte protoporphyrin concentration in 63 patients suffering from chronic renal failure was estimated and found to be significantly decreased when compared to healthy subjects. There was a negative correlation between the decrease of the erythrocyte protoporphyrin and the blood urea and haematocrit. Following haemodialysis the concentration of erythrocyte protoporphyrin was reduced but not significantly so. It is proposed that uraemia or insufficiency of erythropoietin could affect erythroblasts and young red cells impairing haem synthesis.

Localisation and characterisation of egg shell porphyrins in several avian species

1. Electron microscopy, infra-red analysis and histochemical techniques have been used to determine the site of pigment deposition, the cellular localisation of pigment and the type of pigment precipitated in the egg shells of quail, White Leghorn, Brown Ranger and Black-Headed gull. 2. Transfer of pigment occurs via the surface epithelial cells of the shell gland. 3. Porphyrins are probably synthesised in the blood. 4. Possible pigment deposition mechanisms are discussed.