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Query: UNIPROT:P06889 (Mol)
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The single crystals of glycinium oxalate are grown by slow evaporation technique and vibrational spectral analysis is carried out using NIR-FT Raman and FT-IR spectra. The ab initio quantum computations are also performed at HF/6-31 G(d) level to derive the optimized geometry, atomic charges and vibrational frequencies of the glycinium oxalate molecule. Vibrational analysis indicates the presence of peculiar intermolecular C-H...O hydrogen bonding interaction producing "blue shift" of C-H stretching frequency. The vibrational spectra confirm the existence of NH3(+) in glycinium oxalate. Hydroxyl vibrations with different inter and intra molecular H-bonding are analysed, supported by computed results.
Spectrochim Acta A Mol Biomol Spectrosc 2004 Jan
PMID:NIR-FT Raman and infrared spectra and ab initio computations of glycinium oxalate. 1467 Apr 75

Raman spectroscopy has been used to study the thermal transformations of natural magnesium oxalate dihydrate known in mineralogy as glushinskite. The data obtained by Raman spectroscopy was supplemented with that of infrared emission spectroscopy. The vibrational spectroscopic data was complimented with high resolution thermogravimetric analysis combined with evolved gas mass spectrometry. TG-MS identified two mass loss steps at 146 and 397 degrees C. In the first mass loss step water is evolved only, in the second step carbon dioxide is evolved. The combination of Raman microscopy and a thermal stage clearly identifies the changes in the molecular structure with thermal treatment. Glushinskite is the dihydrate phase in the temperature range up to the pre-dehydration temperature of 146 degrees C. Above 397 degrees C, magnesium oxide is formed. Infrared emission spectroscopy shows that this mineral decomposes at around 400 degrees C. Changes in the position and intensity of the CO and CC stretching vibrations in the Raman spectra indicate the temperature range at which these phase changes occur.
Spectrochim Acta A Mol Biomol Spectrosc 2004 Feb
PMID:A Raman spectroscopic study of thermally treated glushinskite--the natural magnesium oxalate dihydrate. 1474 90

The primary hyperoxalurias type 1 (PH1) and type 2 (PH2) are autosomal recessive calcium oxalate kidney stone diseases caused by deficiencies of the metabolic enzymes alanine:glyoxylate aminotransferase (AGT) and glyoxylate/hydroxypyruvate reductase (GR/HPR), respectively. Over 50 mutations have been identified in the AGXT gene (encoding AGT) in PH1, associated with a wide variety of effects on AGT, including loss of catalytic activity, aggregation, accelerated degradation, and peroxisome-to-mitochondrion mistargeting. Some of these mutations segregate and interact synergistically with a common polymorphism. Over a dozen mutations have been found in the GRHPR gene (encoding GR/HPR) in PH2, all associated with complete loss of glyoxylate reductase enzyme activity and immunoreactive protein. The crystal structure of human AGT, but not human GR/HPR, has been solved, allowing the effects of many of the mutations in PH1 to be rationalised in structural terms. Detailed analysis of the molecular aetiology of PH1 and PH2 has led to significant improvements in all aspects of their clinical management. Enzyme replacement therapy by liver transplantation can provide a metabolic cure for PH1, but it has yet to be tried for PH2. New treatments that aim to counter the effects of specific mutations on the properties of the enzymes could be feasible in the not-too-distant future.
Expert Rev Mol Med 2004 Jan 09
PMID:Molecular aetiology of primary hyperoxaluria and its implications for clinical management. 1498 13

Seven highly-coloured lichen species belonging to the genera Caloplaca, Candelariella, Aspicilia and Xanthoria from ecclesiastical buildings in northern Spain have been analysed non-destructively by FT-Raman spectroscopy. The vibrational band assignments in the spectra of the specimens, which were still attached to their limestone or sandstone substrata, were accomplished with the assistance of the chemical compositions obtained from wet chemical extraction methods. beta-Carotene was found in all specimens as the major pigment, and the characteristic spectral signatures of calcium oxalate monohydrate (whewellite) and dihydrate (weddelite) could be identified; chemical signatures were found for these materials even in lichen thalli growing the non-calcareous substrata, indicating, probably, that the calcium was provided here from wind-or-rain-borne sources. The Raman spectral biomarkers found in the lichens broadly agreed with the chemical extraction profiles as expected, but the present study indicates that some form of non-destructive taxonomic identification based on Raman spectroscopy was possible.
Spectrochim Acta A Mol Biomol Spectrosc 2004 Apr
PMID:Lichen biodeterioration of ecclesiastical monuments in northern Spain. 1508 42

A unique feature of the mechanism of iron binding to the transferrin (TF) family is the synergistic relationship between metal binding and anion binding. Little or no iron will bind to the protein without concomitant binding of an anion, physiologically identified as carbonate. Substitution of oxalate for carbonate produces no significant changes in polypeptide folding or domain orientation in the N-lobe of human serum TF (hTF) as revealed by our 1.2A structure. The oxalate is able to bind to the iron in a symmetric bidentate fashion, which, combined with the low pK(a) of the oxalate anion, makes iron displacement more difficult as documented by both iron release kinetic and equilibrium data. Characterization of an N-lobe in which the arginine at position 124 is mutated to alanine reveals that the stabilizing effect of oxalate is even greater in this mutant and nearly cancels the destabilizing effect of the mutation. Importantly, incorporation of oxalate as the synergistic anion appears to completely inhibit removal of iron from recombinant full-length hTF by HeLa S(3) cells, strongly indicating that oxalate also replaces carbonate in the C-lobe to form a stable complex. Kinetic studies confirm this claim. The combination of structural and functional data provides a coherent delineation of the effect of oxalate binding on hTF and rationalizes the results of many previous studies. In the context of iron uptake by cells, substitution of carbonate by oxalate effectively locks the iron into each lobe of hTF, thereby interfering with normal iron metabolism.
J Mol Biol 2004 May 21
PMID:The oxalate effect on release of iron from human serum transferrin explained. 1512 33

The role of Antarctic epilithic lichens in the primary colonization of rocks and in the formation of soils is receiving attention because of the production of the stress-protective biochemicals needed to combat radiation, desiccation and extremes of temperature. Raman microscopy has been used here to study the encrustations produced at the interface between the rock substratum and Buellia spp. lichen thalli; in addition to whewellite, calcium oxalate monohydrate, the presence of weddellite, the metastable dihydrate form, was confirmed in the encrustations. An unusual pigmentation of the rock surface found on detachment of the lichen growths is identified as beta-carotene from its characteristic Raman bands at 1525, 1191, 1157 and 1003 cm(-1); normally, beta-carotene, which has been identified as a UV-radiation protectant, is found at the exposed upper surface of the biological organism. The interface between the detached lichen thalli and the rock also contains whewellite as the sole biomineralization product--which suggests a possible strategy for the formulation of weddelite in the growing Buellia spp. colony as an anti-desiccant.
Spectrochim Acta A Mol Biomol Spectrosc 2004 Jul
PMID:Stratified response to environmental stress in a polar lichen characterized with FT-Raman microscopic analysis. 1524 82

Our structural knowledge of the major facilitator superfamily (MFS) has dramatically increased in the past year with three structures of proteins from the MFS (oxalate/formate antiporter; lactose/proton symporter and the P(i)/glycerol-3-phosphate antiporter). All three structures revealed 12 transmembrane helices forming two distinct domains and could imply that members of the MFS have preserved both secondary as well as tertiary structural elements during evolution. Lactose permease, a particularly well-studied member of the MFS, has been extensively explored by a number of molecular biological, biochemical and biophysical approaches. In this review, we take a closer look at the structure of LacY and incorporate a wealth of biochemical and biophysical data in order to propose a possible mechanism for lactose/proton symport. In addition, we make some brief comparisons between the structures of LacY and GlpT.
Mol Membr Biol
PMID:Lactose permease as a paradigm for membrane transport proteins (Review). 1537 Oct 12

Primary hyperoxaluria type 1 (PH1) is an autosomal recessive disease characterized by progressive kidney failure due to renal deposition of calcium oxalate. The disease is caused by a deficiency of alanine:glyoxylate aminotransferase (AGT) which catalyzes the conversion of glyoxylate to glycine. When AGT is absent, glyoxylate is converted to oxalate which forms insoluble calcium salts that accumulate in the kidney and other organs. In the most common phenotype there is a unique phenomenon wherein AGT is mis-targeted to the mitochondria instead of the peroxisomes. The diagnosis of PH1 is complicated by heterogeneity of clinical presentation, course of the disease, biochemical markers, AGT enzymatic activity and genotype. More than 50 mutations and polymorphisms have been reported in the AGT gene; three common mutations accounting for almost 50% of PH1 alleles. The mutations are of all types, with missense making up the largest fraction. There are some mutations with apparent ethnic associations and at least one that appears to be pan-ethnic. Although correlations can in some cases be made between biochemical phenotype and genotype, correlation with clinical phenotype is complicated by the involvement of other genetic and non-genetic factors that affect disease severity. A number of polymorphisms have been described in the AGT gene some of which cause missense changes and, in some cases, alter enzyme activity. As DNA testing becomes more commonly used for diagnosis it is important to correlate observed sequence changes with previously documented changes as an aid to assessing their potential significance.
Mol Genet Metab
PMID:Genetic heterogeneity in primary hyperoxaluria type 1: impact on diagnosis. 1546 18

The necrotrophic fungal pathogen Sclerotinia sclerotiorum secretes oxalic acid and endo-polygalacturonase (endo-PG) in host plants. Oxalic acid acidifies the plant tissue to values more suitable to endo-PG activity. However, we observed that the infected soybean seedlings possessed a pH of 3.8, which is below that optimal for endo-PG activity (4.5 to 5.0). We investigated, therefore, the effects of pH (from 5.0 to 3.6) and oxalate (5 to 20 mM) on the activity of the major basic endo-PG (PGb) and towards an acidic endo-PG (PGa) secreted by S. sclerotiorum during soybean infection. We verified that only PGb activity is stimulated by oxalate, while at the lowest pH levels, PGa escapes the inhibition of a soybean polygalacturonase-inhibiting protein (PGIP). These results, performed on polygalacturonic acid, were apparently consistent with data obtained from studies with soybean hypocotyl segments, in which PGb activity was increased by oxalate and PGa maintained its activity also at pH 3.6, possibly because at this pH the PGIP contained in the plant tissue is inactive. Reverse transcription-polymerase chain reaction analysis showed that, during soybean infection, the expression of the putative pga gene is delayed in comparison to the basic one. The different temporal expressions of the two endo-PGs and their differing responses to pH, oxalate, and PGIP seem to be consistent with a possible maximization of the fungal PG activity in the host tissue.
Mol Plant Microbe Interact 2004 Dec
PMID:Relationships among endo-polygalacturonase, oxalate, pH, and plant polygalacturonase-inhibiting protein (PGIP) in the interaction between Sclerotinia sclerotiorum and soybean. 1559 46

The quenching effect of L-cysteine and L-methionine on strong chemiluminescence of bis-(2,4,6-trichlorophenyl)oxalate-H(2)O(2) system in the presence of 7-amino-4-trifluoromethylcumarin was studied. The chemiluminescence parameters were evaluated from computer fitting of the resulting intensity-time plots. Both systems resulted in Stern-Volmer plots in the quencher concentration range of 6.5 x 10(-5) to 5.2 x 10(-4)M with k(Q) values of 1.15 x 10(4) and 1.28 x 10(4)M(-1) for L-cysteine and L-methionine, respectively.
Spectrochim Acta A Mol Biomol Spectrosc 2005 Apr
PMID:A study of quenching effect of sulfur-containing amino acids L-cysteine and L-methionine on peroxyoxalate chemiluminescence of 7-amino-4-trifluoromethylcumarin. 1574 Nov 25


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