Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.5.1.61 (porphobilinogen deaminase)
637 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Anemia is a constant complication of uremia. As it has been suggested that uremic toxins (middle molecules) play an important role in the mechanism of anemia, we studied the activities of three heme-synthesizing enzymes: delta-aminolevulinic acid dehydratase, porphobilinogen deaminase and ferrochelatase. In 26 patients on regular dialysis therapy, all three enzymes had significantly lower values than in normal control subjects. From our results, it can be assumed that the decreased heme biosynthesis in chronic uremic patients might be caused by a lack of erythropoietin or by uremic toxins inhibiting erythropoietin and/or heme-synthesizing enzymes.
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PMID:Heme synthesis in anemia of the uremic state. 75 May 46

The effects of human GH and insulin-like growth factor I on the proliferation and differentiation of erythroid progenitor cells from the bone marrow and peripheral blood of children were studied in a hormone-depleted culture system. Growth of erythroid progenitors was quantified by directly scoring colonies and by biochemical determination of the activity of a cytosolic enzyme of the heme pathway, uroporphyrinogen I synthase. In the presence of erythropoietin, high concentrations (50-100 ng/mL) of human GH induced an increase in the number of erythroid colonies (and their uroporphyrinogen I synthase activity) formed by bone marrow or peripheral blood erythroid precursors. In the same conditions, physiological concentrations of insulin-like growth factor I (0.5-1 ng/mL) stimulated erythroid cell growth and differentiation (P less than 0.03) from bone marrow or peripheral blood.
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PMID:Insulin-like growth factor I stimulates human erythroid colony formation in vitro. 358 1

The effect of human somatomedin C/insulin-like growth factor I(SM-C/IGF-1) and human growth hormone (hGH) on colony formation by erythroid precursor cells (CFU-E and BFU-E) from children's bone marrow or blood was studied by methylcellulose cloning assay. We found that physiological concentrations of IGF-1, but not of hGH, stimulated erythropoiesis in vitro in the presence of erythropoietin, as demonstrated by the increased activity of a cytosolic enzyme of the heme pathway (uroporphyrinogen I synthase). The results suggest that IGF-I could be involved in the regulation of erythroid differentiation.
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PMID:[Somatomedin C/insulin-like growth factor I and in vitro erythropoiesis]. 362 55

We studied the effect of natural and synthetic androgens on children's erythropoietic precursor cells in culture. Cultures of normal marrow were carried out according to a miniaturized methylcellulose method in the presence of erythropoietin. We then evaluated the effects of testosterone, nortestosterone, fluoxymesterone and etiocholanolone (10(-9)-10(-6) M) on erythroid colony-forming units (CFU-E) and burst-forming units (BFU-E). Androgen-induced growth of erythroid progenitors was quantified by directly scoring colonies and by a biochemical determination of the uroporphyrinogen I synthase activity (UROS). We observed a significant increase (p less than or equal to 0.05) in the number of CFU-E and BFU-E and in the UROS activity of derived colonies in the presence of androgens (10(-8) or 10(-7)M). This microculture assay could be useful not only to study the effect of androgens on erythroid progenitor cells in culture, but also to predict the best androgenic treatment of anemia in children and adults.
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PMID:Stimulatory effects of androgens on normal children's bone marrow in culture: effects on BFU-E, CFU-E, and uroporphyrinogen I synthase activity. 394 73

Marrow cells induced toward erythroid differentiation by treatment with erythropoietin respond by increasing the rates of iron uptake and hemoglobin synthesis. Study of the enzymes of heme biosynthesis during erythroid differentiation suggests that induction of heme synthesis in these cells is regulated by synthesis of porphobilinogen deaminase. The activities of delta-aminolevulinic acid synthase, gamma, delta-dioxovaleric acid transaminase, delta-aminolevulinic acid dehydratase, and ferrochelatase were not affected significantly by treatment of suppressed marrow cells with erythropoietin over a period of 4 days, whereas that of porphobilinogen deaminase was increased by as much as 3.5-fold by the 3rd day of incubation. The time course of increase in porphobilinogen deaminase activity was parallel to that of the increase in heme synthesis. Moreover, when porphobilinogen deaminase activity was compared in marrow cells exposed to increased levels of erythropoietin in vivo (hyperplastic marrow) and marrow cells exposed to lowered levels of erythropoietin in vivo (suppressed marrow), the activity in the former case was greater than that in normal cells and for the latter type of cell it was lower than normal. Experiments using actinomycin D and cycloheximide suggest that transcription is required for the erythropoietin-induced porphobilinogen deaminase activity, indicating that induction is probably at the level of de novo synthesis of enzyme.
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PMID:The regulation of heme biosynthesis during erythropoietin-induced erythroid differentiation. 401 71

Mouse bone marrow cells infected in vitro with the anemia strain of Friend leukemia virus from large clusters (bursts) of erythroblasts after 5 days in culture in methylcellulose medium. Two types of erythroblast populations can be isolated from bursts of infected cells by manipulation of the culture conditions. One type of erythroblast, which is obtained when erythropoietin (EP) is added to the culture, has proliferated and undergoes differentiation to become an erythrocyte. The second type of erythroblast, which is obtained when no EP is added to the culture, is the product of extensive proliferation, but it fails to undergo the terminal stages of erythroblast differentiation. Comparisons of these two types of erythroblasts demonstrate that specific EP effects include changes in the nucleus, cytoplasm, and membrane of the treated cells. Those events of erythroid differentiation shown to be directed by EP were extrusion of the nucleus from the erythroblast, induction of uroporphyrinogen I synthetase activity, increased iron incorporation into protoporphyrin, synthesis of alpha- and beta-globin polypeptides due largely to increased mRNA production, and synthesis and incorporation of spectrin into the cell membrane. In this system, EP promotes these effects without observable stimulation of progenitor proliferation in addition to that caused by the virus alone. Thus, the role of EP in terminal erythrocyte differentiation is not simply that of an erythroid-specific mitogen.
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PMID:Specific differentiation events induced by erythropoietin in cells infected in vitro with the anemia strain of Friend virus. 695 15

Porphobilinogen is the substrate of two enzymes: porphobilinogen deaminase and porphobilinogen-oxygenase. The first one transforms it into the metabolic precursors of heme and the second diverts it from this metabolic pathway by oxidizing porphobilinogen to 5-oxopyrrolinones. Rat blood is devoid of porphobilinogen-oxygenase under normal conditions while it carries porphobilinogen-deaminase activity. When the rats were submitted to hypoxia (pO2 = 0.42 atm) for 18 days, the activity of porphobilinogen-oxygenase appeared at the tenth day of hypoxia and reached the maximum at the 14-16th day. It decreased to a half after 2 days (half-life of the enzyme) and disappeared after 4 days of return to normal oxygen pressure. Porphobilinogen-deaminase activity increased after the first day of hypoxia, reached a maximum at the 14-16th day and did not decrease to normal values until the 15th day after return to normal oxygen pressure. The activities of both porphobilinogen-oxygenase and porphobilinogen-deaminase were induced by administration of erythropoietin. When rats were made anaemic with phenylhydrazine, porphobilinogen-oxygenase activity also appeared in the blood cells. Although the reticulocyte concentration was higher when compared to that obtained under hypoxia, the activities of the oxygenase obtained under both conditions were comparable. Porphobilinogen-deaminase activity was always closely related to the reticulocyte content. The appearance of porphobilinogenase-oxygenase under the described erythropoietic conditions was due to a de novo induction of the enzyme, as shown by its inhibition with actinomycin D and cycloheximide. Porphobilinogen-oxygenase as well as porphobilinogen-deaminase were present in the rat bone marrow under normal conditions. Their activities increased in phenylhydrazine treated rats. The properties and kinetics of porphobilinogen-oxygenase from the rat blood and bone marrow were determined and found it differ in several aspects.
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PMID:Induction of porphobilinogen oxygenase and porphobilinogen deaminase in rat blood under conditions of erythropoietic stress. 726 Jan 10

Recombinant human erythropoietin (r-HuEPO) is being successfully used for the treatment of uremic anemia. Several abnormalities of heme biosynthetic pathway have been described in patients with end-stage renal failure. In this condition, the activity of erythrocyte porphobilinogen deaminase has been found to be slightly increased. If this enzyme were to be the key enzyme in erythroid heme regulation, its activity would be increased to an even greater degree during the correction of uremic anemia. To assess this hypothesis, this study followed the variations of this and other parameters of porphyrin metabolism over 12 months of erythropoietin therapy in eight patients with nephrogenic anemia who underwent hemodialysis. By the first month of therapy, an increase of the previously depressed erythrocyte activity of aminolevulinate dehydratase was already evident, in coincidence with a nonsignificant increase of the reticulocyte count. The activity of this enzyme reached its maximal level by Month 3, and did not change up to Month 10. The porphobilinogen deaminase hyperactivity normalized at Month 4. By Month 12, in coincidence with the reduction of erythropoietin doses, the maximal levels of erythrocyte protoporphyrin, and the decrease in aminolevulinate dehydratase activity, the porphobilinogen deaminase values started to increase once again. In conclusion, the administration of r-HuEPO to hemodialyzed patients induced transient normalization of the previously observed porphyrin metabolism abnormalities. However, erythrocyte porphobilinogen deaminase activity did not rise concomitantly with the increase in hematocrit or hemoglobin values, but it did diminish during treatment. Therefore, porphobilinogen deaminase did not behave as a controlling enzyme in heme synthesis during the r-HuEPO-induced correction of uremic anemia.
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PMID:Effects of recombinant human erythropoietin on porphyrin metabolism in uremic patients on hemodialysis. 873 13

The porphyrias are inherited or acquired metabolic disorders caused by a partial deficiency in one of the enzymes of the heme biosynthetic pathway. Eight enzymes are utilized in the synthesis of heme. An enzyme defect in one of the last seven enzymes will result in one of the seven different forms of porphyria, some of which have similar signs and symptoms. This article describes six diabetic, azotemic patients with no prior history of porphyria, who developed a syndrome similar to acute intermittent porphyria after initiation of treatment with erythropoietin. One of the patients developed the syndrome predialysis, whereas the remaining patients were on maintenance hemodialysis. The symptoms varied but all resolved when erythropoietin was discontinued and reappeared in four cases when erythropoietin was restarted. In all of the patients, the enzyme aminolevulinic acid-dehydratase (ALA-D) was low and the uroporphyrinogen synthase was normal. This enzyme abnormality suggests an acquired form of delta-aminolevulinic acid dehydratase porphyria (ADP). Lead toxicity, succinylacetone, and zinc deficiency are known to depress ALA-D, but these conditions were not present. The development of the acute porphyria syndrome while the patients were receiving pharmacological doses of erythropoietin, which resolved when the drug was stopped, suggests that by stimulating heme synthesis, erythropoietin may unmask an enzyme deficiency resulting in the clinical expression of ADP. The patients responded favorably to a regimen that included discontinuation of erythropoietin, tight blood sugar control, maintaining the hematocrit above 30%, and a KT/V, a measure of dialysis adequacy, of 1.5 in the hemodialysis group. Plasmapheresis accelerated the recovery when used in two patients.
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PMID:Porphyria syndrome associated with diabetic nephrosclerosis and erythropoietin. 1743 69

Anemia is a major clinical symptom of a wide variety of pathological conditions a common related to reduced erythropoiesis. Whereas erythropoietin treatment showed an improvement in the patients' condition, it revealed increased risks of thromboembolic and cardiovascular events. Herein we describe stimulation of erythropoiesis by the multifunctional 1-(butyryloxy)ethyl-5-amino-4-oxopentanoate, (AlaAcBu), a 5-aminolevulinic-acid (ALA) derivative, which undergoes metabolic hydrolysis yielding two erythroid differentiation inducers, ALA and butyric acid (BA), each acting through a different mechanism. ALA, the first precursor in the heme biosynthesis, accelerates heme synthesis and BA, a histone deacetylase inhibitor (HDACI) that activates the transcription of globin mRNA. Our results show that the AlaAcBu mutual prodrug is a potent chemical differentiation inducer of K562 human erythroleukemia cells manifested by augmentation of heme and globin synthesis and assembly of hemoglobin. Exposure of K-562 cells to AlaAcBu resulted in an increase in heme synthesis and globin expression. Stimulation of the heme pathway was evident by the over-expression of porphobilinogen deaminase (PBGD) and ferrochelatase. AlaAcBu promoted cellular erythroid differentiation depicted by the expression of the marker glycophorin A and cellular maturation characterized by cytoplasm hemoglobinization, polar arrangement of mitochondria and a developed central vacuolar system preceding nuclear extrusion. The ability of AlaAcBu to promote differentiation along the erythroid lineage and to dramatically induce hemoglobin synthesis presented in this report.
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PMID:A multifunctional 5-aminolevulinic acid derivative induces erythroid differentiation of K562 human erythroleukemic cells. 2270 51


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