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At least 379 records · Page 21Linked to original sources
PubMed1990

The role of reduced glutathione during the course of acute haemolysis in glucose-6-phosphate dehydrogenase deficient patients: clinical and pharmacodynamic aspects.

Tissue hypoperfusion leads to cellular oxidative and peroxidative damage due to biochemical disorders in the oxygen and substrate metabolism. The metabolic turnover of glutathione (GSH) represents one the main cytoprotective systems against the peroxide attack and the depletion or defect in resynthesis of this compound is accompanied by pathological consequences. In the present study the clinical effects of glutathione depletion were investigated in conditions of acute tissue hypoxia due to marked haemolysis in glucose-6-phosphate dehydrogenase deficient patients (favism syndrome). In these subjects a significant marker of the tissue oxidative damage was represented by the uric acid blood levels, presumably linked to xanthine-hypoxanthine altered metabolism. To antagonize the effects of oxyradical pathology, reduced glutathione was administered to a group of patients and the results confirmed the cytoprotective role played by the GSH supplementation. The GSH action was evident on the tissue metabolism and this supports the opinion that reduced glutathione could represent a new and interesting therapeutic approach in marked and acute hypoxic conditions.

Adolescent↗
PubMed1996

Independent origin of single and double mutations in the human glucose 6-phosphate dehydrogenase gene.

The vast majority of both polymorphic and sporadic G6PD variants are due to single missense mutations. In the four polymorphic variants that have two point mutations, one of the mutations is always 376 A-->G (126 Asn-->Asp), which on its own gives rise to the nondeficient polymorphic variant, G6PD A. In a study of G6PD deficient patients who presented with clinical favism in Spain, we have found a new polymorphic variant that we have called G6PD Malaga, whose only abnormality is a 542 A-->T (181 Asp-->Val) mutation. This is the same mutation as previously found in association with the mutation of G6PD A in the double mutant, G6PD Santamaria. G6PD Malaga is associated with enzyme deficiency (class III), and the enzymic properties of G6PD Malaga and G6PD Santamaria are quite similar, indicating that in this case the effects of the two mutations are additive rather than synergistic. G6PD Santamaria might have been produced by recombination between G6PD A and G6PD Malaga; however haplotype analysis, including the use of a new silent polymorphism, suggests that the same 542 A-->T mutation has taken place independently in a G6PD B gene to give G6PD Malaga and in a G6PD A gene to give G6PD Santamaria. These findings help to outline the relationship and evolution of mutations in the human G6PD locus.

Amino Acid Sequence↗
PubMed1991

[The degradation of vicine and convicine in field bean meal by selected bacterial strains].

Vicine and convicine as natural occurring toxic compounds in Vicia faba are involved in the formation of hemolytic anemia (favism). Removal of these compounds needs high technological expense. Microbiological degradation with different strains of bacteria was tried. After 3 h incubation with Streptococcus faeciens convicine was converted completely and Vicine to about 95%.

Biodegradation, Environmental↗
PubMed2006

CAPs markers to assist selection for low vicine and convicine contents in faba bean (Vicia faba L.).

The antinutritional factors (ANFs) present in Vicia spp. seeds are a major constraint to the wider utilization of these crops as grain legumes. In the case of faba bean (Vicia faba L.), a breeding priority is the absence vicine and convicine (v-c); responsible for favism in humans and for the reduced animal performance or low egg production in laying hens. The discovery of a spontaneous mutant allele named vc-, which induces a 10-20 fold reduction of v-c contents, may facilitate the process. However, the high cost and difficulty of the chemical detection of v-c seriously restricts the advances in breeding-selection. To identify random amplified polymorphic DNA (RAPD) markers linked to this gene, we have analysed an F(2 )population derived from a cross between a line with high v-c content (Vf6) and the vc- genotype (line 1268). Quantification of v-c was done by spectrophotometry on the parents and the F(2 )population (n = 136). By using bulked segregant analysis (BSA), two RAPD markers linked in coupling and repulsion phase to the allele vc- were identified and further converted into sequence characterized amplified regions (SCARs). Amplification of SCARS was more consistent, although the initial polymorphism between pools was lost. To recover the polymorphisms several approaches were explored. Restriction digestion with HhaI (for SCAR SCH01(620)) and RsaI (for SCAR SCAB12(850)) revealed clear differences between the parental lines. The simultaneous use of the two cleavage amplified polymorphism (CAP) markers will allow the correct fingerprinting of faba bean plants and can be efficiently used in breeding selection to track the introgression of the vc- allele to develop cultivars with low v-c content and improved nutritional value.

Animals↗
PubMed1985

Hexose monophosphate shunt-stimulated reduction of methemoglobin by divicine.

Reduced divicine (2,6-diamino-4,5-dihydroxypyrimidine), an aglycone implicated in the pathogenesis of favism, reduces methemoglobin efficiently in intact erythrocytes and in hemolysates. Oxidized divicine produces the same effect when glucose or an NADPH-generating system is added to intact erythrocytes or to hemolysates. Although NADPH, NADH, and GSH have no direct methemoglobin-reducing activity in vitro, they convert oxidized divicine to the reduced hydroquinone species, which is responsible for the electron transfer to methemoglobin. Reduction of methemoglobin is optimally observed under nitrogen since, in the presence of oxygen, reduced divicine undergoes autoxidation. Several lines of evidence rule out the reduction of methemoglobin by divicine through an enzyme-catalyzed process, although it is certainly sustained by the hexose monophosphate shunt activity of erythrocytes through the generation of both NADPH and GSH. Thus, the strong enhancing effect that glucose produces on the divicine-dependent methemoglobin reduction within intact normal erythrocytes is completely absent in erythrocytes from glucose-6-phosphate dehydrogenase-deficient subjects. This distinctive behavior might account for the enhanced methemoglobin levels that are found both in vitro in glucose-6-phosphate dehydrogenase-deficient erythrocytes exposed to divicine and in vivo as a typical feature of the acute hemolytic crisis of favic patients.

Catalase↗
PubMed1986

Oxidative inactivation of the calcium-stimulated neutral proteinase from human red blood cells by divicine and intracellular protection by reduced glutathione.

Calpain, the micromolar Ca2+-requiring form of Ca2+-stimulated neutral proteinase purified from human red cells, is remarkably inactivated during autoxidation of divicine (2,6-diamino-4,5-dihydroxypyrimidine), an aglycone implicated in the pathogenesis of favism. Inactivation of purified calpain is produced, in decreasing order of efficiency, by transient, probably semiquinonic species arising from autoxidation of divicine, by the H2O2 that is formed upon autoxidation itself, and by quinonic divicine, respectively. Purified procalpain, the millimolar Ca2+-requiring form that can be converted to the fully active calpain form by a variety of mechanisms, is less susceptible than calpain itself to inactivation by the same by-products of divicine autoxidation. When intact red cells are exposed to autoxidizing divicine, procalpain undergoes a significant loss of activity. At 1 mM divicine, intracellular inactivation is observed with procalpain only, while the activity of a number of red cell enzymes is unaffected. Inactivation of procalpain is consistently greater in red cells from glucose-6-phosphate dehydrogenase-deficient subjects than in normal cells. Restoration of normal levels of glucose-6-phosphate dehydrogenase activity by means of entrapment of homogeneous human glucose-6-phosphate dehydrogenase in the deficient red cells results in normal stability of intracellular reduced glutathione; decreased susceptibility of procalpain to inactivation by autoxidizing divicine. These findings suggest that in the glucose-6-phosphate dehydrogenase-deficient red cells the procalpain-calpain system is a major target of divicine cytotoxicity.

Calpain↗
PubMed1985

Divicine induces calcium release from rat liver mitochondria.

Divicine, a pyrimidine aglycone strongly implicated in the pathogenesis of favism, induces calcium release from intact rat liver mitochondria. Divicine-dependent calcium release is accompanied by oxidation and hydrolysis of intramitochondrial pyridine nucleotides. Inhibition of both mitochondrial glutathione peroxidase and glutathione reductase slows down divicine-induced calcium release. Cyanide-insensitive respiration indicates redox cycling of divicine in mitochondria. The results suggest that attention should be paid to the action of divicine in cells other than red blood cells.

Animals↗
PubMed1988

Glutathione reductase-deficient erythrocytes as host cells of malarial parasites.

BCNU [1,3-bis(2-chloroethyl)-1-nitrosourea] and its less toxic derivative HeCNU [1-(2-chloroethyl)-3-(2-hydroxyethyl)-1-nitrosourea] are clinically-used antitumour drugs. In erythrocytes BCNU is a highly specific inhibitor of the enzyme glutathione reductase [H. Frischer and T. Ahmad, J. Lab. clin. Med. 89, 1080 (1977)]. When treating erythrocytes in vitro, 50% enzyme inhibition was obtained with 1 microM BCNU or 3 microM HeCNU within 2 hr. The two drugs were used for preparing red cell populations with various levels of glutathione reductase activity; complete inhibition (greater than or equal to 98%) was only achieved when the medium contained glucose as a source of reducing equivalents. The erythrocytes were then tested in drug-free media as host cells for the malaria parasite Plasmodium falciparum. In the range of 0-300 mU/ml cells, there was a correlation between glutathione reductase activity and parasite growth; erythrocytes with an activity of less than 20 mU/ml did not serve as host cells for P. falciparum at all although these erythrocytes were viable. When the culture medium was supplemented with 20 mM glutathione (GSH), parasite growth was normal irrespective of the glutathione reductase level in the erythrocytes. This is consistent with the finding that poisoning glutathione reductase led to a 10-fold decrease of the cytosolic GSH level. Our results corroborate the concept that intraerythrocytic inhibition of glutathione reductase mimicks the biochemistry of drug-sensitive glucose-6-phosphate dehydrogenase deficiency (favism), an inherited condition which confers protection from malaria.

Animals↗
PubMed2006

Prevalence of erythrocyte glucose-6-phosphate dehydrogenase (G6PD) deficiency in the population of western Turkey.

BACKGROUND: Newborn G6PD deficiency screening has been recognized as an essential component of public health care in most developed and some Mediterranean countries. However, such screening is yet to be widely embraced in Turkey. The aim of the present study was to determine the normal values of G6PD and deficiency prevalence of this enzyme in different age groups of people living in the western region of Turkey and accordingly inform and educate about favism to those asymptomatic carriers who usually are not aware of their G6PD deficient status. METHODS: A total of 1421 clinically healthy individuals without evidence of leukocytosis or thrombocytosis were included in the study. Activity of G6PD was quantitatively measured. RESULTS: Normal mean values of G6PD in healthy males were 8.94 +/- 8.65 IU/g Hb (or 231.73 +/- 43.16 IU/10(12) RBC), in females were 9.16 +/- 3.78 IU/g Hb (or 219.9 +/- 43.1 IU/10(12) RBC). The frequencies of severe and mild G6PD deficiencies were 0.44% and 6.07% in females, respectively, whereas in males it was 7.24%. Overall frequency of the G6PD-deficient phenotype was detected as 6.9%. CONCLUSIONS: There is no significant statistical difference of G6PD activity between males and females, although frequency of the G6PD-deficient phenotype is relatively high in western Turkey. The results emphasize a need for screening for G6PD deficiency before prescribing anti-malarial therapy with drugs like primaquine to patients in this region of Turkey known for its prevalence of malaria.

Erythrocytes↗
PubMedDate not supplied

Distinct phenotypic expression of two de novo missense mutations affecting the dimer interface of glucose-6-phosphate dehydrogenase.

Mutations encoding class I glucose-6-phosphate dehydrogenase (G6PD) variants are associated with chronic nonspherocytic hemolytic anemia (CNSHA), the most severe phenotypic expression of G6PD deficiency. These mutations frequently affect the G6PD dimer interface that is essential for enzymatic activity. We detected two de novo missense mutations concerning residues located close together in the dimer interface in two patients with severe G6PD deficiency. A novel c.1225C>T missense mutation was identified in a male neonate who presented with hemolysis and severe hyperbilirubinemia and the predicted Pro409Ser substitution constituted a novel class I variant, designated G6PD Utrecht. G6PD deficiency in the second patient was due to the once previously reported class I variant G6PD Sumaré (Val431Gly). Structural analysis revealed that the mutated residues Pro409 and Val431, located on different subunits, interact directly across the subunit interface and perturb formation of the G6PD dimer upon mutation. Favism and mild chronic hemolysis characterized the phenotype of the patient with G6PD Sumaré which contrasts with the more severe clinical picture of the patient with G6PD Utrecht and, in addition, that of the patient originally described with G6PD Sumaré. We postulate that this G6PD variant is at the crossing between class I and class II G6PD deficiency and its ultimate phenotypic expression is either aggravated or ameliorated by other (extra)genetic factors.

Binding Sites↗
PubMedDate not supplied

Molecular heterogeneity of glucose-6-phosphate dehydrogenase (G6PD) variants in the south of Thailand and identification of a novel variant (G6PD Songklanagarind).

Two hundred and twenty-five G6PD-deficient subjects in Songklanagarind Hospital in the south of Thailand comprising 210 males and 15 females were studied. Neonatal jaundice was detected in 85% of these patients. Acute hemolysis related to infection was detected in 17.3% of the G6PD-deficient subjects. Drug-induced acute hemolysis was detected in 1.8% and favism was observed in 3.6% of G6PD-deficient patients. The molecular analysis was performed on 134 G6PD-deficient individuals by a combination of PCR-RFLP, multiplex polymerase chain reaction by multiple tandem forward primers and a common reverse primer assay (MPTP) and DNA sequencing to characterize the mutations of the samples with abnormal MPTP bands. We found 10 different missense G6PD mutations and the three most common variants were G6PD Viangchan 871,G-->A (31.3%), G6PD Kaiping 1388,G-->A (20.1%) and G6PD Mahidol 487,G-->A (17.2%) followed by G6PD Canton 1376,G-->T (9.7%), G6PD Union 1360,C-->T (2.2%), G6PD Gaohe 95,A-->G (1.5%), G6PD Quing Yuan 392,G-->T (0.7%), G6PD Mediterranean 563,C-->T (0.7%), G6PD Songklanagarind 196,T-->A (0.7%), silent mutation 1311,C-->T (6.7%), and uncharacterized variant (9%). A novel missense mutation at codon 196, TTC-->ATC in exon 4 of the G6PD gene predicting a single amino acid substitution, Phe66Ile was identified and we designated this novel class II variant as G6PD Songklanagarind. The G6PD variants among the Thais in the southern part are heterogeneous and G6PD Viangchan, Kaiping, Mahidol, and Canton variants account for about 78% of the cases. Our findings provide some evidence that G6PD Viangchan and Mahidol are common Southeast Asian variants and support the theory of genetic drifts throughout Southeast Asia.

Female↗
PubMed2006

Molecular characterization of glucose-6-phosphate dehydrogenase deficiency in the Kurdish population of Western Iran.

A total of 1,000 school boys ages 14-18 years, were randomly selected from six schools of Kermanshah and screened for G6PD deficiency. Fifty-three out of 1,000 were found to be severely G6PD deficient giving a frequency of 5.3% for G6PD deficiency in males in Kermanshah. We performed DNA analysis on 68 G6PD deficient children, 52 school boys and 16 children with the history of favism and hemolytic anemia using a combination of PCR-RFLP technique, single strand conformation polymorphism (SSCP) analysis and DNA sequencing. Three polymorphic G6PD mutations were identified: G6PD Mediterranean, Chatham and Cosenza. The commonest allele was found to be the G6PD Mediterranean (91.2%) followed by the G6PD Chatham (7.3%) and the G6PD Cosenza (1.5%). Haplotype analysis revealed that 56 out of 62 (90%) G6PD Mediterranean was linked to haplotype BclI(+) (1311T). In contrast, all G6PD Chatham and Cosenza had haplotype BclI(-) (1311C). The polymorphism IVS11-93 (T-->C) was present in 88.5% of the subjects studied. Only 4/55 (7.3%) of the Mediterranean alleles were associated with the T form and were always related to the nt 1311C. Our findings indicate that the allele frequency of G6PD Mediterranean mutation in Kermanshah is higher than those from two Fars ethnic groups living in Northern and Southern Iran. Nevertheless, they are in strict accordance with a previous report of the prevalence of the G6PD Mediterranean in Kurdish and Middle East population. Also, of strong association of the G6PD Mediterranean mutation and the presence of the polymorphism nt 1311C-->T in the Kermanshah population demonstrate that the presence of this mutation may be the result of migrations that have taken place through the history of Iran.

Adolescent↗
PubMed1984

The interaction of divicine with glutathione and pyridine nucleotides.

Native divicine , a pyrimidine aglycone strongly implicated in the pathogenesis of favism, undergoes rapid auto-oxidation according to a 1:1 stoichiometry with respect to the oxygen disappeared. In the presence of oxygen divicine re-oxidizes both NADPH and NADH, whereby a red-ox cycling is perpetuated between hydroquinonic and quinonic species of divicine itself. The oxygen-dependent interaction of divicine with GSH involves a 90% oxidation to GSSG and the parallel formation of two distinct adducts. Both adducts have been isolated by means of HPLC and characterized in their spectral properties. The one having maximum absorption at 305 nm is susceptible of reduction by glutathione reductase, while the adduct with maximum absorption at 320 nm is stable and is likely to represent a dead-end complex of divicine .

Chemical Phenomena↗
PubMed2000

Human glucose-6-phosphate dehydrogenase: the crystal structure reveals a structural NADP(+) molecule and provides insights into enzyme deficiency.

BACKGROUND: Glucose-6-phosphate dehydrogenase (G6PD) catalyses the first committed step in the pentose phosphate pathway; the generation of NADPH by this enzyme is essential for protection against oxidative stress. The human enzyme is in a dimer<-->tetramer equilibrium and its stability is dependent on NADP(+) concentration. G6PD deficiency results from many different point mutations in the X-linked gene encoding G6PD and is the most common human enzymopathy. Severe deficiency causes chronic non-spherocytic haemolytic anaemia; the usual symptoms are neonatal jaundice, favism and haemolytic anaemia. RESULTS: We have determined the first crystal structure of a human G6PD (the mutant Canton, Arg459-->Leu) at 3 A resolution. The tetramer is a dimer of dimers. Despite very similar dimer topology, there are two major differences from G6PD of Leuconostoc mesenteroides: a structural NADP(+) molecule, close to the dimer interface but integral to the subunit, is visible in all subunits of the human enzyme; and an intrasubunit disulphide bond tethers the otherwise disordered N-terminal segment. The few dimer-dimer contacts making the tetramer are charge-charge interactions. CONCLUSIONS: The importance of NADP(+) for stability is explained by the structural NADP(+) site, which is not conserved in prokaryotes. The structure shows that point mutations causing severe deficiency predominate close to the structural NADP(+) and the dimer interface, primarily affecting the stability of the molecule. They also indicate that a stable dimer is essential to retain activity in vivo. As there is an absolute requirement for some G6PD activity, residues essential for coenzyme or substrate binding are rarely modified.

Amino Acid Sequence↗
PubMedDate not supplied

Chemical analysis and hemolytic activity of the fava bean aglycon divicine.

Divicine is an unstable aglycon metabolite of the fava bean pyrimidine beta-glucoside vicine. Divicine has long been thought to be a mediator of an acute hemolytic crisis, known as favism, in susceptible individuals who ingest fava beans (Vicia faba). However, a recent report has questioned the chemical identity of the divicine that was used in most of the studies on divicine hemotoxicity. The present study was undertaken to examine the hemolytic potential of synthetic divicine. Divicine was synthesized and its identity and purity were confirmed by HPLC, mass spectrometry, and NMR spectroscopy. The stability and redox behavior of divicine, under physiological conditions, were examined by HPLC and cyclic voltammetry. The data indicate that divicine is readily oxidized under aerobic conditions; however, it was sufficiently stable at pH 7.4 to permit its experimental manipulation. When 51Cr-labeled rat erythrocytes were exposed in vitro to the parent glucoside, vicine (5 mM), and then readministered to rats, no decrease in erythrocyte survival was observed. In contrast, erythrocyte survival was dramatically reduced by in vitro exposure to divicine (1.5 mM). These data demonstrate that divicine is a direct-acting hemolytic agent and thus may be a mediator of the hemolytic crisis induced by fava bean ingestion.

Animals↗
PubMed2000

Glucose-6-phosphate dehydrogenase deficiency.

Glucose-6-phosphate dehydrogenase (G6PD) is expressed in all tissues, where it catalyses the first step in the pentose phosphate pathway. G6PD deficiency is prevalent throughout tropical and subtropical regions of the world because of the protection it affords during malaria infection. Although most affected individuals are asymptomatic, there is a risk of neonatal jaundice and acute haemolytic anaemia, triggered by infection and the ingestion of certain drugs and broad beans (favism). A rare but more severe form of G6PD deficiency is found throughout the world and is associated with chronic non-spherocytic haemolytic anaemia. Many deficient variants of G6PD have been described. DNA sequence analysis has shown that the vast majority of these are caused by single amino acid substitutions. The three-dimensional structure of G6PD shows a classical dinucleotide binding domain and a novel beta + alpha domain involved in dimerization.

Anemia, Hemolytic, Congenital Nonspherocytic↗
PubMed2002

[Isolated decrease of haptoglobin during pregnancy: diagnosis by chance or pathological? ].

Haptoglobin is an acute-phase-protein, which is important in many diseases like infections, trauma and neoplasma. An increase in haptoglobin is induced by cytocines like IL-6 und IL-1. The normal range for plasmatic haptoglobin is 50-220 mg/dl. During pregnancy the most likely diagnosis is the HELLP- Syndrome (hemolysis, elevated liver enzymes and low platelets), followed by rare diagnoses like viral hepatitis or favism. We report about a 31-year-old III-gravida 0-para at 31 weeks of gestation with a decrease of haptoglobin over a period of 6 weeks (cut off: < 13 mg/dl) and without any clinical signs of preeclampsia. Liver enzymes were constantly slightly elevated without any progress, other laboratory test results were normal. The patient had a caesarean section at 37 weeks of gestation. Serum haptoglobin returned to normal values within three days after delivery. The reason for the decrease of haptoglobin in our case remains uncertain. Further studies need to focus on the differential diagnosis of a decrease of haptoglobin as well as an isolated decrease of haptoglobin during pregnancy and on the valid ranges of the different haptoglobin subtypes.

Adult↗
PubMed1996

Neonatal jaundice in Saudi newborns with G6PD Aures.

Sixty-five of 3261 (2%) Saudi neonates were found to be severely G6PD-deficient during a cord blood screening programme conducted from April to December, 1992. However, at the time of molecular studies, the blood samples were available from only 20 randomly selected children, aged from 1 to 6 years. DNA analyses showed that seven (three boys, four girls) of these 20 (35%) had G6PD Aures (nt 143 T - > C), a variant associated with favism which was recently reported in an Algerian. Twelve carried the G6PD Mediterranean (563 T) mutation, and in one child the mutation remained unidentified. The medical records of these children showed that all who had G6PD Aures, including a premature baby, were jaundiced during the 1st week of life, but only six full-term infants had moderate-to-severe hyperbilirubinaemia. Two of seven babies had seizures and one of these two developed kernicterus, in spite of timely blood transfusion.

Base Sequence↗