. Biochemistry of plants and animals, an introduction. Biochemistry. 470 ANIMAL BIOCHEMISTRY jjoitaiit components ol the animal itscll both as the blood pigment hemoglobin and as respiratory jjroteins like catalase. Since red cells, tor example, have a relatively limited life, some provision must be made ior disposing of the hemoglobin liberated. Thus animals have both external and internal supplies of such materials to excrete or to make use of according to their needs and capabilities. Most animals anci birds appear to synthesize all the porphyrin they need for hemoglobin from glycine and su
. Biochemistry of plants and animals, an introduction. Biochemistry. 470 ANIMAL BIOCHEMISTRY jjoitaiit components ol the animal itscll both as the blood pigment hemoglobin and as respiratory jjroteins like catalase. Since red cells, tor example, have a relatively limited life, some provision must be made ior disposing of the hemoglobin liberated. Thus animals have both external and internal supplies of such materials to excrete or to make use of according to their needs and capabilities. Most animals anci birds appear to synthesize all the porphyrin they need for hemoglobin from glycine and succinyl coenzyme A. They do not utilize porphyrins from their diets to a significant extent. Isotope studies indicate that all the atoms of protoporphyrin come from glycine and succinate, revealing the very close connection be- tween reactions already discussed and porphyrin synthesis. HgNCHgCOO" + "OOCCH2CH2CO—CoA ^~OOCCH2CH2COCHCOO + CoA NH3+ a-ainino-/3-ketoadipate glycine succinyl coenzyme A -OOCCH2 +H3NCH2 CHaCHzCOO^ CH. CH2 COOH CH2- HOOCCH2. ; "OOCCH2CH2COCH2NH3"*' 5-aminolevulinic acid hemoglobin CH=CH2 protoporphyrin After an average life of aboiu 125 days, erythrocytes are destroyed in human beings by cells in the spleen, liver, and bone marrow. The overall process leads to return of the globin to the amino acid pool and to excretion of degradation products of the porphyrin. Iron is carried by the plasma to the iron-storage system for later use. The porphyrin is converted to bile pigments which accompany the bile into the intestine and are excreted in the feces. Small quantities of bile pigments appear in the urine, amounting to 1 to 2 mg. daily. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Mallette, M. Frank (Manney Frank), 1917-. New York, Wiley
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