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)

Assay of erythrocyte uroporphyrinogen I synthase is an accepted diagnostic test for acute intermittent porphyria, particularly in those individuals who are asymptomatic or in whom the disease is not biochemically manifested by excretion of excess porphyrin precursor. The assay described is based upon a coupled-enzyme procedure in which added delta-aminolevulinic acid and its dehydratase present in erythrocytes are used to generate porphobilinogen as substrate for uroporphyrinogen synthase. Zinc and dithiothreitol are added with preincubation to give maximum activity and reproducibility. These agents also prevent inhibition by lead. Healthy young women had a mean activity of 40 nmol of porphyrin formed per milliliter of erythrocytes per hour, men and activity of 38 nmol/ml/h. Preparation of control specimens is described. This assay gave within-day CVs ranging from 1.9 to 2.8%. Precautions in interpretation of results are discussed.
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PMID:Modified erythrocyte uroporphyrinogen I synthase assay, and its clinical interpretation. 69 83

Some parameters of haem synthesis were estimated in 60 uraemic patients (30 non-dialysed, 30 dialysed) and in 30 matched controls. Serum delta-aminolaevulinic acid and erythrocyte coproporphyrin and protoprophyrin were found significantly higher in the non-dialysed uraemics than in the controls. Erythrocyte delta-aminolaevulinic acid dehydrase (ALA-D) activity was 498 +/- 174 mumol/h.l in the non-dialysed patients, 321 +/- 146 in the dialysed (just before haemodialysis) and 833 +/- 281 in the healthy controls, the differences between these groups all being statistically significant (p less than 0.001). After haemodialysis the enzymic activity in the dialysed group increased significantly (380 +/- 167, p less than 0.001), but remained lower than normal (p less than 0.001). A similar pattern - although with less statistical significance of the differences between groups - was observed concerning erythrocyte uroporphyrinogen I synthase activity. Incubation of normal erythrocytes with uraemic plasma resulted in a considerable decrease of their ALA-D activity (from 830 +/- 263 to 616 +/- 126) while incubation of uraemic erythrocytes with normal plasma increased their ALA-D (from 384 +/- 139 to 494 +/- 77). Addition of zinc in the haemolysate caused a similar induction of ALA-D in both controls and uraemics. The zinc-induced uraemic ALA-D practically reached normal levels. The mechanism of enzymic depression and the possible role of elevated delta-aminolaevulinic acid concentrations (to which depressed ALA-D activity considerably contributes) in the pathogenesis of the neurologic manifestations of uraemia, are discussed.
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PMID:Some parameters of haem synthesis in dialysed and non-dialysed uraemic patients. 285 53

Uroporphyrinogen III synthase (hydroxymethylbilane hydro-lyase (cyclizing); EC 4.2.1.75), the fourth enzyme in the heme biosynthetic pathway, was purified to homogeneity from human erythrocytes. For enzyme purification and characterization, a sensitive coupled enzyme assay was used which generated the substrate, hydroxymethylbilane; the oxidized product, uroporphyrin III, was quantitated by high pressure liquid chromatography. Uroporphyrinogen III synthase was initially separated from delta-aminolevulinate dehydratase and hydroxymethylbilane synthase by a preparative anion exchange chromatographic step. Subsequent chromatography on hydroxyapatite, phenyl-Sepharose, and Sephadex G-100 purified the enzyme about 70,000-fold with an 8% yield. Homogeneous enzyme was obtained following a final C4-reversed phase high pressure liquid chromatographic step which removed a single major and several minor protein contaminants from the enzyme. The purified enzyme had a specific activity of over 300,000 units/mg, an isoelectric point of 5.5, and was thermolabile (t1/2 at 60 degrees C approximately 1 min). Molecular weight studies by gel filtration (Mr approximately equal to 30,000) and analytical sodium dodecyl sulfate-polyacrylamide gel electrophoresis (Mr approximately equal to 29,500) were consistent with the enzyme being a monomer. Using hydroxymethylbilane as substrate, the purified enzyme formed uroporphyrinogen III in the absence of hydroxymethylbilane synthase or other cofactors. The pH optimum was 7.4 and the Km for hydroxymethylbilane was 5-20 microM. The enzyme was activated by Na+, K+, Mg+, and Ca2+ and was inhibited by Cd2+, Cu2+, Hg2+, and Zn2+. Amino acid composition analysis was performed, and the N-terminal sequence, Met-Lys-Val-Leu-Leu-Leu, was determined by microsequencing. The availability of the purified enzyme should permit investigation of its reaction mechanism as well as facilitate biochemical and molecular studies of the genetic defect in congenital erythropoietic porphyria.
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PMID:Purification and properties of uroporphyrinogen III synthase from human erythrocytes. 380 19

Unexpected differences in clinical and biochemical findings in two brothers occupationally exposed to the same source of lead for dissimilar lengths of time are presented. Only the brother with the shorter period of lead exposure was anemic and afflicted by nausea, vomiting, abdominal colic and arthralgia. His urinary PBG output yielded the high orders of magnitude found in acute intermittent porphyria in relapse. Prior to administration of a single dose of EDTA (1 g of the calcium disodium salt given intravenously in 325 mL 0.15 mol/L NaCl), his blood lead levels averaged 3.6 mumol/L. The amount of chelatable lead retrieved from his urine, 31 mumol/day, was more than twice that found in his asymptomatic counterpart who was exposed to lead for 13 months and whose pre-EDTA blood lead levels averaged 4.0 mumol/L. Not only the activity of delta-aminolaevulinic acid dehydratase, but also that of uroporphyrinogen I synthetase, was markedly inhibited by lead in red cells of both brothers. These activities were restored to normal levels in vitro by addition to the assay system of zinc and dithiothreitol. This ruled out a coexisting genetic deficiency of either enzyme. The anemia of the symptomatic brother with the shorter period of lead exposure was alleviated by folic acid, 15 mg/day. The differences in findings between the two brothers point to differential susceptibility to lead and illustrate the extent to which symptomatic lead poisoning may mimic biochemical and clinical features of the acute porphyrias.
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PMID:Occupational lead exposure: studies in two brothers showing differential susceptibility to lead. 401 20

A spectrophotometric method for porphobilinogen deaminase assay in erythrocytes is described. This test is determinant for the definite diagnosis of acute intermittent porphyria. In the method described, delta-aminolevulinic acid is used as substrate. Mercaptoethanol and zinc ions are introduced to maintain delta-aminolevulinic acid dehydratase in optimal conditions and to guarantee the in vitro production of porphobilinogen. An incubation temperature of 45 degrees C leads to the production of uroporphyrins, which are measured spectrophotometrically at 405 nm, giving reproducible results. The assay can be performed easily in any clinical laboratory and is valuable for detecting both patients and carriers of acute intermittent porphyria.
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PMID:A modified spectrophotometric assay for porphobilinogen deaminase: its application in the detection of both carriers and patients with acute intermittent porphyria. 762 45

The haem biosynthesis pathway continues to provide surprises, from the first enzyme, 5-aminolaevulinic acid synthase, the mRNA of which contains an iron-responsive element, to the last, ferrochelatase, that contains an iron sulphur cluster. 5-Aminolaevulinate dehydratase from animals are zinc-dependent enzymes while those from plants require magnesium. The first X-ray structure of a haem synthesis enzyme, porphobilinogen deaminase, has not only yielded clues about the mechanism of tetrapyrrole assembly but has also provided insight into the molecular basis of the human disease acute intermittent porphyria. Evidence is growing to suggest that a previously unsuspected alternative haem pathway may exist.
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PMID:Highlights in haem biosynthesis. 771 94

Two alternatives for the treatment of lead intoxication, administration of zinc or a thiol donor, S-adenosyl-L-methionine (SAM), were analysed. Rats were exposed to lead (Pb)-acetate (60 mg/l) in drinking water during 90 days; one group also received SO4Zn in water (40 mg/l), while another received both Pb and SAM (5 mg/24 hr intraperitoneally. Erythrocytic delta-aminolaevulinic dehydratase (ALA-D) activity was significantly reduced (P < 0.001) both in rats receiving Pb alone and in rats receiving Pb and each of the other two treatments. The high erythrocytic uroporphyrinogen synthetase (URO-S) activity noticed in Pb administered rats, was significantly (P < 0.001) reduced in animals treated either with zinc or with SAM. Hepatic ALA-D activity tended to decrease while renal enzyme activity was not modified by the low level Pb exposure used in this work. Interestingly, SAM treated rats in both tissues exhibited significantly (P < 0.01) higher activities of the enzyme. It is argued that SAM treatment causes a surplus of thiols that allows the full expression of ALA-D catalytic activity.
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PMID:Effect of zinc or S-adenosyl-l-methionine on long term administration of low doses of lead to rats. 829 45

The study was aimed to assess the protective efficacy of zinc against hemo and hematotoxicity induced by lead. Two groups of 8 rats each, were administered lead acetate 20 mg/kg bw (ip) for 3 days. One group in addition was injected 5 mg/kg bw (ip) zinc acetate for next three days. A third group of 8 rats was given three injections of normal saline and served as control. All the animals were sacrificed on eighth day and assessed for hematological changes, heme synthesizing pathway enzymes, hepatic drug metabolizing status and sulfhydryl levels in blood and liver. Lead administration resulted in decreased hemoglobin, increased reticulocytosis, depression of delta aminolevulinic acid dehydratase (ALAD) and uroporphyrinogen I synthetase (UPS) activity in blood and liver. In vitro metabolism of drugs aminopyrine, aniline and p-nitroanisole by liver homogenate and in vivo metabolism of pentabarbitone was also reduced in lead exposed rate. Zinc treated rats showed improved hematological profile and activated ALAD and UPS activity, recovery of N-demethylation of aminopyrine and O-demethylation of p-nitroanisole and partial restoration of free thiol levels in blood and liver thereby indicating that zinc could confer protection against lead toxicity.
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PMID:Preventive action of zinc against lead toxicity. 858 50

The effect of beryllium (Be) compounds on porphyrins was investigated in pregnant mice. The blood protoporphyrin (Proto) and zinc protoporphyrin (Zn Proto) concentrations were increased in pregnancy. Regardless of pregnancy or nonpregnancy, the Proto concentration was decreased after Be injection. Delta-aminolevulinic acid dehydratase (ALA-D) and porphobilinogen deaminase (PBG-D) activities in blood were significantly elevated in the pregnant untreated (Con-pregnant) group, compared to the nonpregnant mice untreated (Con-nonpregnant) and nonpregnant mice treated with Be (Be-nonpregnant) groups. The blood ALA-D activity of the pregnant mice treated with Be (Be-pregnant group) tended to decrease, compared to Con-pregnant group. The blood PBG-D activity in the Be-pregnant group was significantly lower compared with that of the Con-pregnant group. The ALA-D and PBG-D activities in the spleen were also significantly elevated in the Con-pregnant group, compared to nonpregnant groups. However, it was noted that these values in the Be-pregnant group were almost the same as that of the Con-nonpregnant group and were significantly lower than that in the Con-pregnant group. The elevation of ALA-D and PBG-D activities in the blood and spleen, which play a role in the hematopoietic function of mice, was observed in the Con-pregnant mice compared to the nonpregnant mice. However, the phenomenon was not observed in the Be-pregnant mice, it suggesting that Be suppressed the pregnancy-induced increase in hematopoietic function.
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PMID:Effect of beryllium chloride on porphyrin metabolism in pregnant mice administered by subcutaneous injection. 914 Apr 67

Beryllium chloride and/or zinc chloride were intraperitoneally injected into mice. The amount of beryllium (Be) injected corresponded to 1/10th of the LD50 dose intravenously administered. The amount of zinc (Zn) injected was the same as Be. The changes in porphyrin metabolism of the mice were studied. Delta-aminolevulinic acid dehydratase (ALA-D) activities in the blood were found to increase significantly in Zn and BeZn groups when compared to the control level. The blood porphobilinogen deaminase (PBG-D) activity in the Zn group was slightly less than that in the controls. The ALA-D and PBG-D activities in liver were higher in the Be and BeZn groups than in the controls. The splenic ALA-D activities were significantly higher in the Zn and BeZn groups than in the control and Be groups. The splenic PBG-D activities were markedly higher in the Be and/or Zn groups than in the controls. An increase in ALA-D activities in the blood and spleen was observed in the BeZn group, together with an increase in ALA-D activities caused by Zn administration. Furthermore, the increase in PBG-D activities in liver and spleen was observed in the Be and/or Zn groups. The results suggested that chemical similarity between Be and Zn brought about these phenomena.
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PMID:[Changes in porphyrin metabolism of mice given beryllium and/or zinc]. 921 91


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