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Porphyrin heme biosynthesis

W.O. Whetsell Jr., S. Sassa, D. Bickers, A. Kappas (1978). Studies on porphyrin-heme biosynthesis in organotypic cultures of chick dorsal root ganglion. I. Observations on neuronal and non-neuronal elements. J. Neuropath. Exp. Neurol., 37, 497-507. [Pg.97]

This IS used for synthesis of porphobilinogen fEq 10 24 Porphobilinogen is the key building block in the biosynthesis of pigments of life such as porphyrins, heme, and vitamin Interestmg application of porphobdiogen to synthesis of immunocomponents for the measurement of lead fPb by fluorescence polarizadon Immunoassay has been reported "... [Pg.332]

A summary of the steps in the biosynthesis of the porphyrin derivatives from PBG is given in Figure 32-8. The last three enzymes in the pathway and ALA synthase are located in the mitochondrion, whereas the other enzymes are cytosolic. Both erythroid and non-erythroid ( housekeeping ) forms of the first four enzymes are found. Heme biosynthesis occurs in most mammalian cells with the exception of mature erythrocytes, which do not contain mitochondria. However,... [Pg.271]

Hematological Effects. The effects of lead on the hematopoietic system have been well documented. These effects, which are seen in both humans and animals, include increased urinary porphyrins, coproporphyrins, ALA, EP, FEP, ZPP, and anemia. The process of heme biosynthesis is outlined in Figure 2-10. Lead interferes with heme biosynthesis by altering the activity of three enzymes ALAS,... [Pg.261]

Tissues that synthesize heme, and the sources of porphyrin s carbon and nitrogen The major sites of heme biosynthesis are the liver (where the rate of synthesis is highly variable) and the erythrocyte-producing cells of the bone marrow (where the rate is generally constant). All the carbon and nitrogen atoms are provided by glycine and succinyl CoA. [Pg.493]

Within the past few years, there has been considerable progress in understanding the role played by the mitochondria in the cellular homeostasis of iron. Thus, erythroid cells devoid of mitochondria do not accumulate iron (7, 8), and inhibitors of the mitochondrial respiratory chain completely inhibit iron uptake (8) and heme biosynthesis (9) by reticulocytes. Furthermore, the enzyme ferrochelatase (protoheme ferro-lyase, EC 4.99.1.1) which catalyzes the insertion of Fe(II) into porphyrins, appears to be mainly a mitochondrial enzyme (10,11,12,13, 14) confined to the inner membrane (15, 16, 17). Finally, the importance of mitochondria in the intracellular metabolism of iron is also evident from the fact that in disorders with deranged heme biosynthesis, the mitochondria are heavily loaded with iron (see Mitochondrial Iron Pool, below). It would therefore be expected that mitochondria, of all mammalian cells, should be able to accumulate iron from the cytosol. From the permeability characteristics of the mitochondrial inner membrane (18) a specialized transport system analogous to that of the other multivalent cations (for review, see Ref. 19) may be expected. The relatively slow development of this field of study, however, mainly reflects the difficulties in studying the chemistry of iron. [Pg.83]

Woods, J.S., Fowler, B.A. (1978). Altered regulation of mammalian hepatic heme biosynthesis and urinary porphyrin excretion during prolonged exposure to sodium arsenate. Toxicol. Appl. Pharmacol. 43(2) 361-71. [Pg.134]

The porphyrias are a heterogeneous group of diseases, all of which involve disorders of heme biosynthesis, which result in accumulation and increased excretion of porphyrins or porphyrin precursors. The porphyrias can be divided into two kinds the hereditary porphyrias, some of which can be exacerbated by exposure to certain chemicals, and the toxic porphyrias, which can be produced by exposure to certain chemicals alone. The pattern of excretion of porphyrins and porphyrin precursors is characteristic for each type. Clinical symptoms consist mainly of cutaneous photosensitivity and/or neurological disturbances. Hexachlorobenzene is a chemical inducer of porphyria. [Pg.1553]

The principal tissues involved in heme biosynthesis are the hematopoietic tissues and the liver. Biosynthesis requires participation of eight enzymes, of which four (the first and the last three) are mitochondrial and the rest are cytosolic (Figure 29-4). The reactions are irreversible. Glycine and succinate are the precursors of porphyrins. [Pg.684]

The porphyrias are a group of disorders caused by abnormalities in heme biosynthesis. They are inherited and acquired disorders characterized by excessive accumulation and excretion of porphyrins or their precursors. Defects in any one of the eight enzymes involved in heme biosynthesis may cause inherited porphyrin-related disorders (Figure 29-9). Porphyrins have a deep red or purple color (Greek porphyra = purple). Porphyrins are... [Pg.686]

Porphyria—A group of disorders involving heme biosynthesis, characterized by excessive excretion of porphyrins or their precursors may be inherited or may be acquired, as from the effects of certain chemical agents. [Pg.2689]

We devised a screen for isolating mutants defective in iron-dependent regulation of heme biosynthesis that did not require prior knowledge of the mechanism or of the rate-limiting steps [83]. We speculated that if the pathway as a whole were regulated by iron, a mutant defective in that control would accumulate protoporphyrin under iron limitation. Mutants defective in the heme synthesis enzymes ferrochelatase [75] or protoporphyrinogen oxidase would likely have a similar phenotype, but porphyrin accumulation would likely be independent of iron in the structural gene mutants, and those strains would also be expected to be heme auxotrophs. [Pg.7]

J. Ho, R. Gutherie, H. Tieckelmann (1986). Detection of (5-aminolevulinic acid, porphobilinogen and porphyrins related to heme biosynthesis by high performanee liquid chromatography. J. Chromatogr., 375, 56-63. [Pg.97]

The next step in heme biosynthesis, is the condensation of two molecules of ALA, via the enzyme ALA dehydratase, to give the pyrrole called porphobilinogen or PBG. This compound was first identified in the urine of patients suffering from one of a family of diseases of porphyrin metabolism, called porphyrias. Labelled PBG has been efficiently incorporated into heme using chicken blood as the biosynthetic model system. What is interesting about the biosynthesis of PBG is that it is very similar... [Pg.31]


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See also in sourсe #XX -- [ Pg.19 , Pg.20 , Pg.21 , Pg.22 ]




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