Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q00604 (X-linked)
 16,883 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of a single interaperitoneal injection (6 mg/kg body weight) of aflatoxin B1 in propylene glycol on pyridine nucleotides and NDP linked dehydrogenases was studied 24 h after administration of the toxin. The liver showed a decrease in total proteins and pyridine nucleotides though levels of NADP and NADPH remained unchanged. Levels of NAD and NADH were decreased. The activities of hepatic of hwpRIX of hepatic malate dehydrogenase (MDH) and isocitrate dehydrogenase (ICDH) were not altered though ICDH showed an increase when expressed on protein basis. However, there was a significance decrease in the activity of combined HMP dehydrogenases. Adipose tissue showed increased activities of the HMP dehydrogenasess.
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PMID:Effect of aflatoxin B1 on pyridine nucleotides and NADP linked dehydrogenases. 0 75

The NADPH oxidase of phagocytic cells is important for the efficient killing and digestion of ingested microbes. A very unusual low-potential cytochrome b (b-245) is the only redox molecule to have been identified in this system. The FAD-containing flavoprotein that binds NADPH and transfers electrons to the cytochrome has eluded identification for three decades. We show here that the haem/FAD ratio in the membranes does not change significantly on activation of this oxidase, indicating that the FAD is present in the membranes from the outset and not recruited from the cytosol. The FAD content of membranes from cells of patients with X-linked chronic granulomatous disease (CGD) lacking the cytochrome b was roughly one-quarter of that in normal subjects and in autosomal recessive CGD patients lacking the cytosolic protein p47-phox. Similar low amounts of FAD were present in uninduced promyelocytic (HL60) cells, suggesting that the low amount of FAD in cells from X-CGD patients was probably unrelated to this oxidase system. Cytochrome b-245 appears to bind both the haem and FAD, in a molar ratio of 2:1. The e.p.r. signal of the purified cytochrome was weak and had an asymmetric g(z) peak at g = 3.31. The purified cytochrome could be partially reflavinated (about 20%) in the presence of lipid. Amino acid sequence homology was detected between the beta-subunit of this cytochrome b and the ferredoxin-NADP+ reductase (FNR) family of reductases in the putative NADPH- and FAD-binding sites. 32P-labelled 2-azido-NADP was used as a photoaffinity label for the NADPH-binding site. Labelling that was competed off with NADP was observed in the region of the beta-subunit of the cytochrome. No labelling was seen in this region in X-CGD in three subjects in whom this cytochrome was missing and in a third in whom it was present but bore a Pro-His transposition in the putative NADPH-binding site. These studies indicate that cytochrome b-245 is a flavocytochrome, the first described in higher eukaryotic cells, bearing the complete electron-transporting apparatus of the NADPH oxidase.
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PMID:Cytochrome b-245 is a flavocytochrome containing FAD and the NADPH-binding site of the microbicidal oxidase of phagocytes. 132 Mar 78

Ribonucleotide reductase from Escherichia coli catalyzes the conversion of nucleotides to deoxynucleotides. Multiple cysteins have been postulated to play a key role in this process. To test the role of various cysteines in nucleotide reduction, a variety of single and double mutants of the R1 subunit were prepared: C754S, C759S, C754-759S, C462S, C462A, C230S, and C292S. Due to the expression system, each mutant contains small amounts of contaminating wt-R1 (estimated to be 1.5-3% based on activity). An epitope tagging method in conjunction with anion exchange chromatography was used to partially resolve the mutant R1 from the wt-R1. The interaction of these mutants with the normal substrate was studied, which allowed a model to be proposed in which five cysteines of the R1 subunit of RDPR play a role in catalysis. C754S and C759S R1s catalyze CDP formation at rates similar to wt-R1 when DTT is used as a reductant. However, when thioredoxin (TR)/thioredoxin reductase (TRR)/NADPH is used as reductant, the rates of dNDP production are similar to those expected for contaminating wt-R1 present as a heterodimer with the mutant. The impaired nature of these mutants with respect to reduction by TR suggests that their function is to transfer reducing equivalents from TR to the active site disulfide of R1 produced during NDP reduction. Single-turnover experiments, designed to avoid the problem of contaminating wt-R1, also support this role for C754 and C759. The double serine mutant of 754 and 759 has catalytic activity with DTT that is one-third the rate of wt-R1 with thioredoxin. C225 and C462 are thought to be the active site cysteines oxidized concomitantly with NDP reduction. Conversion of these cysteines to serines results in R1 mutants which convert the normal substrate into a mechanism-based inhibitor. C462SR1 upon incubation with R2 and [3'-3H,U-14C]UDP results in uracil release, 3H2O production, 3H,14C-labeled protein which has an absorbance change at 320 nm, and slow loss of the tyrosyl radical on R2. The isotope effect (kH/k3H) on 3' carbon-hydrogen bond cleavage is 1.7. This sequence of events is independent of the reductant, consistent with the postulate that C462 is an active site thiol. The C462AR1 has properties similar to C462SR1. Several additional mutant R1s, C230SR1, and C292SR1 were shown to have activities similar to wt-R1 with both TR/TRR/NADPH and DTT.
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PMID:A model for the role of multiple cysteine residues involved in ribonucleotide reduction: amazing and still confusing. 138 92

Five male patients from four different families presented with a clinical record of chronic granulomatous disease (CGD): recurrent infections of the skin and/or respiratory tract with catalase-positive microorganisms, sometimes in combination with granulomata and/or abscesses in various organs. These patients differed from "classical" forms of the disease in that their neutrophils, although deficient in killing in vitro of Staphylococcus aureus, contained a decreased but measurable amount of cytochrome b558 (10-60% of normal on a heme basis), causing weak staining in the nitroblue tetrazolium dye test and a depressed respiratory burst after contact of the cells with fluid or particulate activators of the NADPH:O2 oxidoreductase. In the cell-free activation system, the defect in the patients' cells was localized in the membrane fraction. In each of the four families, the cellular abnormalities showed an X-linked inheritance. Fusion experiments performed with the monocytes from these patients and those from patients with classical X-linked, cytochrome b558-negative (Xb(0)) or autosomal, cytochrome b558-positive (Ab+) CGD showed complementation of NADPH:O2 oxidoreductase activity in the latter but not in the former combination. Thus, the unusual CGD patients represent variant forms of Xb(0) CGD, with mutations in the gene coding for the beta subunit of cytochrome b558 that do not cause complete loss of this protein.
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PMID:Chronic granulomatous disease with partial deficiency of cytochrome b558 and incomplete respiratory burst: variants of the X-linked, cytochrome b558-negative form of the disease. 143 53

The NADPH:O2 oxidoreductase of phagocytic leukocytes is an important enzyme for the bactericidal activity of these cells. Cytochrome b558 is a membrane component of this enzyme. In X-linked chronic granulomatous disease (Xb- CGD) the phagocytes are defective in the beta-subunit (gp91-phox) of this cytochrome. We have studied the genetic defect in a group of six X-linked CGD patients characterized by complete or partial loss of cytochrome b558 with the use of the polymerase chain reaction. All patients had a different single point mutation in the gp91-phox gene, indicating that the genetic defect in Xb- CGD is very heterogeneous. In one patient the mutation leads to a premature termination codon. In the other five cases these mutations predict incorporation of a different amino acid. The mutations were with one exception found in the N-terminal half of the protein, suggesting that this part of cytochrome b558 is important for the binding of the heme or for formation of a stable complex with p22-phox. Two histidyl residues were found that might be ligands of the heme iron.
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PMID:Point mutations in the beta-subunit of cytochrome b558 leading to X-linked chronic granulomatous disease. 171 Jan 53

This study was aimed at determining whether the peripheral benzodiazepine receptor (PBZDR), which is abundantly expressed on mononuclear phagocytes, is involved in host defense mechanisms depending on phagocyte membrane-associated NADPH-oxidase complex. Analysis by reversible and covalent binding of PBZDR expression on human neutrophils shows that it is modulated during NADPH-oxidase activation with phorbol 12-myristate 13-acetate. Based on a series of 17 patients with chronic granulomatous disease (CGD), results show that PBZDR expression is dramatically impaired in X-linked CGD, an inherited disorder due to a mutation on the gene coding for cytochrome b558 NADPH-oxidase component, whereas it is unaffected in autosomal recessive CGD where cytochrome b558 is normally expressed, suggesting a link between PBZDR and cytochrome b558 expressions. PBZDR can be assigned by covalent binding to an 18-Kd membrane protein. These results suggest that the neutrophil PBZDR, which can accommodate the widely prescribed anxiolytic drug Valium (diazepam), is involved in host defense against pathogens, a function that could be affected by neuroimmune interactions.
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PMID:Altered expression of neutrophil peripheral benzodiazepine receptor in X-linked chronic granulomatous disease. 216 94

A membrane-bound cytochrome b, a heterodimer formed by a 91-kD glycoprotein (heavy chain) and a 22-kD polypeptide (light chain), is an essential component of the phagocyte NADPH-oxidase responsible for superoxide generation. Cytochrome b is absent in two subgroups of chronic granulomatous disease (CGD), an inherited disorder characterized by the lack of oxidase activity. Mutations in the cytochrome heavy chain gene, encoded by the CYBB locus in Xp21.1, result in the X-linked form of CGD. A rare subgroup of autosomal recessive CGD also lacks cytochrome b (A- CGD), but the genetic defect has not previously been identified. In order to search for possible mutations in the cytochrome light chain locus, CYBA, the structure of this gene was characterized. The CYBA locus was localized to 16q24, and the approximately 600-bp open reading frame determined to be encoded by six exons that span approximately 8.5 kb. Three unrelated patients with A- CGD were studied for evidence of mutations in the light chain gene. One patient, whose parents were first cousins, was homozygous for a large deletion that removed all but the extreme 5' coding sequence of the gene. The other two patients had a grossly normal light chain transcript on Northern blot of mononuclear cell RNA. The light chain transcript was amplified by the polymerase chain reaction and sequenced. One patient was a compound heterozygote for two alleles containing point mutations in the open reading frame that predict a frame shift and a nonconservative amino acid replacement, respectively. The second patient, whose parents were second cousins, was homozygous for a different single-base substitution resulting in another nonconservative amino acid change. These results indicate that A- CGD can results from defects in the gene encoding the 22-kD light chain of the phagocyte cytochrome b.
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PMID:Human neutrophil cytochrome b light chain (p22-phox). Gene structure, chromosomal location, and mutations in cytochrome-negative autosomal recessive chronic granulomatous disease. 224 41

Monoclonal antibodies (MoAbs) were raised against cytochrome b558, a membrane-bound component of the NADPH:O2 oxidoreductase in human neutrophils. This cytochrome consists of a low-molecular-weight (low-mol-wt) subunit of 22 to 23 Kd, probably encoded by an autosomal gene, and a high-mol-wt subunit of 75 to 90 Kd, encoded on the X-chromosome. MoAb 449 reacts with the low-mol-wt subunit and MoAb 48 with the high-mol-wt subunit on Western blots of purified cytochrome b558 and on blots of whole neutrophil extracts. In extracts of neutrophils from patients with chronic granulomatous disease (CGD) in which cytochrome b558 is not detectable by spectrophotometric methods, the low-mol-wt subunit is present, albeit in a much smaller amount. The high-mol-wt subunit is not detected by MoAb 48 in neutrophils of patients with X-linked CGD and in neutrophils of patients with the autosomal, cytochrome-b558-negative form of the disease. These results can be explained by a marked instability of these subunits when the synthesis of either of the two is disturbed. In differentiated HL-60 cells, the high-mol-wt subunit appears to be present in a different form. Cloning of the low-mol-wt subunit with the help of MoAb 449 suggests the presence of a heme-binding site on this subunit. By comparison of the binding characteristics of MoAb 449 to intact and permeabilized neutrophils with those of MoAb 7D5, recently isolated by Nakamura et al (Blood 69:1404, 1987), the low-mol-wt subunit was established as a transmembrane protein.
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PMID:Characterization of two monoclonal antibodies against cytochrome b558 of human neutrophils. 246 97

A membrane-bound cytochrome b, a heterodimer formed by a 91-kD glycoprotein and a 22-kD polypeptide, is a critical component of the phagocyte NADPH-oxidase responsible for the generation of superoxide anion. Mutations in the gene for the 91-kD chain of this cytochrome result in the X-linked form of chronic granulomatous disease (CGD), in which phagocytes are unable to produce superoxide. Typically, there is a marked deficiency of the 91-kD subunit and the cytochrome spectrum is absent (X- CGD). In a variant form of CGD with X-linked inheritance, affected males have a normal visible absorbance spectrum of cytochrome b, yet fail to generate superoxide (X+ CGD). The size and abundance of the mRNA for the 91-kD subunit and its encoded protein were examined and appeared normal. To search for a putative mutation in the coding sequence of the 91-kD subunit gene, the corresponding RNA from an affected X+ male was amplified by the polymerase chain reaction and sequenced. A single nucleotide change, a C----A transversion, was identified that predicts a nonconservative Pro----His substitution at residue 415 of the encoded protein. Hybridization of amplified genomic DNA with allele-specific oligonucleotide probes demonstrated the mutation to be specific to affected X+ males and the carrier state. These results strengthen the concept that all X-linked CGD relates to mutations affecting the expression or structure of the 91-kD cytochrome b subunit. The mechanism by which the Pro 415----His mutation renders the oxidase nonfunctional is unknown, but may involve an impaired interaction with other components of the oxidase.
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PMID:A missense mutation in the neutrophil cytochrome b heavy chain in cytochrome-positive X-linked chronic granulomatous disease. 255 53

Glucose-6-phosphate dehydrogenase (G6PD) has a major role in NADPH production and is found in almost all cell types. The structural gene for G6PD is X-linked in Drosophila melanogaster, as it is in most eukaryotic organisms, and due to its ubiquitous expression, it can be considered a typical 'housekeeping' gene. Here we present the complete nucleotide (nt) sequence of G6PD cDNAs as well as the genomic copy of the G6PD gene. The G6PD gene has three introns so that the protein-coding region is divided into four segments. The 5'-end of mature G6PD mRNA is located 289 +/- 1 nt upstream from the start codon. The sequence upstream from the transcription start point is G + T-rich and contains no commonly found transcription regulatory elements, such as a TATA box or GGGCGG sequence. D. melanogaster G6PD is 65% homologous with the human G6PD protein but has no homology with the human sequence for the first 42 amino acid residues. The G6PD gene was shown to be active when transduced to autosomal positions. For each transformant, G6PD activity in both male and female adults was not significantly different, indicating that the transduced gene, unlike the resident G6PD, is not dosage-compensated in males.
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PMID:Nucleotide sequence of the Drosophila glucose-6-phosphate dehydrogenase gene and comparison with the homologous human gene. 283 91


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