Absence Of Borate Research Articles

Jasmonate signaling and remodeling of cell wall metabolism induced by boron deficiency in pea shoots

Boron (B) is an essential element for plant growth but its cellular functions are poorly defined. We conducted transcriptome analysis of shoot apices of pea ( Pisum sativum L.) growing for up to 18 days in the presence or absence of borate. Shoots of B deficient plants exhibited impaired elongation of the apex but increased growth of lateral shoots. Transcriptome analysis at days 10, 14 and 18 revealed 42, 517 and 2684 differentially expressed genes (DEGs), respectively, relating to diverse aspects of cell growth, metabolism, membrane function and cell signaling. Genes involved in jasmonate signaling and cell wall metabolism were upregulated in the B deficient plants. Many DEGs encoded transcription factors (TFs) potentially involved in these responses including many MYB and ethylene-responsive transcription factor (ERF) proteins and two orthologs of MYC2 which has been implicated in jasmonate signaling. Treatment of detached apices with B or jasmonic acid (JA) led to rapid changes in the expression of several of these DEGs. These results are consistent with a major role for borate in cell wall structure, perturbation of which can activate jasmonate signaling and cell wall remodeling. Such changes can help to explain how B deficiency leads to changes in shoot growth and architecture. • Boron deficiency leads to impaired growth of the shoot apex in pea plants. • Boron deficiency activates jasmonate signaling. • Boron deficiency causes widescale changes in expression of genes for cell wall components and metabolism.

Crystal structure of günterblassite, a new mineral with a triple tetrahedral layer

57 Postmagmatic parageneses of the Eifel volcanic field (Germany) are characterized by a wide variety of minerals [1]. Gunterblassite 1 is a new mineral discov� ered in a late association formed in the cavities of the alkaline basalt of the Rother Kopf mountain. The chemical composition was determined by electron microprobe analysis. The content of H 2 O was quanti� fied by chromatographic analysis of gaseous products of calcination. The IR spectrum of the mineral shows the absence of borate, carbonate, nitrate, and ammo� nium groups. The empirical formula calculated for 13 atoms (Si, Al) is

NaBC1 Is a Ubiquitous Electrogenic Na +-Coupled Borate Transporter Essential for Cellular Boron Homeostasis and Cell Growth and Proliferation

Boron is a vital micronutrient in plants and may be essential for animal growth and development. Whereas the role of boron in the life cycle of plants is well documented, nothing is known about boron homeostasis and function in animal cells. NaBC1, the mammalian homolog of AtBor1, is a borate transporter. In the absence of borate, NaBC1 conducts Na + and OH − (H +), while in the presence of borate, NaBC1 functions as an electrogenic, voltage-regulated, Na +-coupled B(OH) 4 − transporter. At low concentrations, borate activated the MAPK pathway to stimulate cell growth and proliferation, and at high concentrations, it was toxic. Accordingly, overexpression of NaBC1 shifted both effects of borate to the left, whereas knockdown of NaBC1 halted cell growth and proliferation. These findings may reveal a previously unrecognized role for NaBC1 in borate homeostasis and open the way to better understanding of the many presumed physiological roles of borate in animals.

Recognition control of the nucleic acid model through conformational switching of nucleobase induced by borate ester formation of cis-2',3'-diol.

A novel nucleic acid model that possessed 5'-amino-5'-deoxyuridine at alpha- and gamma-position of L-glutamic acid through amide linkage using 5'-amino group was synthesized and the conformation and the hybridization properties were studied. The complex of alpha-PRNA with complementary DNA/RNA was more stable than the corresponding natural duplex in the absence of borate. Its recognition ability was however lost when borax was added to the solution.

Metal ion sequestering by borate-(amino)polyhydroxy oxime systems in aqueous solution; a 11B, 13C and 113Cd NMR study

Cu(II) and Cd(Il) coordination to mixtures of (amino)polyhydroxy oximes and borate has been studied using 11B, 113C and 113Cd NMR and titration procedures. The (amino)polyhydroxy oximes have strong Cu(II) coordinating properties, also in the absence of borate. The polyhydroxy oximes, on the contrary, have only low Cd(II) sequestering abilities. The metal ion complexing abilities of D-Glucosamine oxime can be enhanced by the addition of borate. D-Glucosamine oxime forms borate diesters in which the borate is bound to the threo-3,4 diol functions. This species coordinates Cd(II) via the E isomers of both ligands by two oxime (or oximato) and two amino groups, while probably also two borate oxygens assist in the Cd(II) complexation. Factors determining metal ion coordination by borate diesters are discussed.

The Influence of Arginine-specific Reagents on Nitrate Uptake by Corn Seedlings

The effects of three arginine-specific reagents on NO3 uptake were studied using corn seedlings (Zea mays L., Golden Cross Bantam). In the presence of borate, 0-25 mM 2,3-butanedione (BD) and 10 mM 1,2-cyclohexanedione (CHD) inhibited NO3 uptake by 76% and 68%, respectively, compared to the controls. However, in the absence of borate, only 18% and 38% inhibition was observed for 0-25 mM BD and 1-0 mM CHD, respectively. Similarly, 0-5 mM phenylglyoxal (PGO) resulted in 75% inhibition. The degree of inhibition of nitrate uptake exhibited a concentration-dependence with respect to the reagents. Corn seedlings are 2- or 3-fold more sensitive to BD than to PGO and CHD, respectively, presumably due to the unfavourable steric effects of the benzal ring. Uptake of NO3 was partially restored after removal of BD, CHD, and PGO from the uptake medium. No significant differences were observed for the ATPase and plasma membrane-associated vanadate-sensitive H+-ATPase or K+-stimulated ATPase activity in homogenates and microsomal fractions prepared from corn seedlings which had been incubated for 2 h in the presence or absence of 0-5 mM BD or 10 mM PGO. This suggests that inhibition of nitrate uptake by the arginine specific reagents was not caused by the indirect effect of their binding and inhibiting H+-ATPase. The fact that the arginine specific reagents strongly inhibit NOi uptake indicates that the NO^ transport system has arginine residues at or near the active site.

Modification of an arginine residue essential for the activity of NAD-malic enzyme from Ascaris suum

Purified NAD-malic enzyme from Ascaris suum is rapidly inactivated by the arginine reagent, 2,3-butanedione, and this inactivation is facilitated by 30 m m borate. Determination of the inactivation rate as a function of butanedione concentration suggests a second-order process overall, which is first order in butanedione. A second-order rate constant of 0.6 m −1 s −1 at pH 9 is obtained for the butanedione reaction. The inactivation is reversed by removal of the excess reagent upon dialysis. The enzyme is protected against inactivation by saturating amounts of malate in the presence and absence of borate. The divalent metal Mg 2+ affords protection in the presence of borate but has no effect in its absence. The nucleotide reactant NAD + has no effect on the inactivation rate in either the presence or absence of borate. A dissociation constant of 24 m m is obtained for E:malate from the decrease in the inactivation rate as a function of malate concentration. An apparent K i of 0.5 m m is obtained for oxalate (an inhibitor competitive vs malate) from E:Mg:oxalate while no significant binding is observed for oxalate using the butanedione modified enzyme. The pH dependence of the first-order rate of inactivation by butanedione gives a p K a of 9.4 ± 0.1 for the residue(s) modified, and this p K is increased when NAD is bound. The arginine(s) modified is implicated in the binding of malate.

Synthesis of pyridoxine-β-glucoside by rice bran β-glucosidease and its in situ absorption in rat small intestine

A major component of β-glucosidase multi-enzymes was highly purified from rice bran, and by its use, PIN-β-G was synthesized from p-nitrophenyl-β-glucoside and pyridoxine. The synthetic product contained both 4′- and 5′-isomers, which were successfully separated by high-voltage paper electrophoresis. The 4′-isomer was used as a convenient subsrate for intestinal absorption of PIN-β-G, because it gave a positive reaction with 2,6-dibromoquinone chlorimide irrespective of the presence or absence of borate. The absorption experiments with in situ isolated rat jejunal loops revealed that the PIN-β-G level remaining in the loop did not significantly change within an hour and that δ-gluconolactone, a potent inhibitor of β-glucosidase, did neither affect the luminal disappearance of PIN-β-G. It thus can be assumed that PIN-β-G is absorbed across the intestinal wall by a mechanism of simple diffusion, but not of “hydrolase-mediated transport”.

β‐Glucosidase of Penicillium funiculosum. I. Purification

A strain of Penicillium funiculosum, isolated in this laboratory, produced in high yield both endo- and exo-glucanases and beta-glucosidases, which were suitable for the saccharification of cellulosic materials. The isolation of the beta-glucosidase of this organism, which differs from other beta-glucosidases of fungi in its substrate specificity, by preparative electrophoresis, is described in this article. The organism was grown on a lactose-casein medium and the culture filtrate concentrated by ammonium sulfate precipitation and dialysis. Electrophoresis was carried out on large slabs of polyacrylamide gel in an anodicrun in the presence of borate at pH 7. After elution of active fractions, a cathodic run was made at pH 6.0. Two precipitations with ammonium sulfate resulted in a homogeneous enzyme (specific activity 174 IU/mg). A second isozyme was also produced by P. funiculosum on cellulose-wheat bran medium. This isozyme was purified by electrophoresis at pH 7.0 in the absence of borate and was obtained free from other isozymes of beta-glucosidase and cellulases.

Essential arginyl residues in the H+-translocating ATPase of plasma membrane from the yeast Schizosaccharomyces pombe.

The H+-translocating adenosine-5'-triphosphatase (ATPase) purified from the yeast Schizosaccharomyces pombe is inactivated upon incubation with the arginine modifier 2,3-butanedione. The inactivation of the enzyme is maximal at pH values above 8.5. The modified enzyme is reactivated when incubated in the absence of borate after removal of 2,3-butanedione. The extent of inactivation is half maximal at 10 mM 2,3-butanedione for an incubation of 30 min at 30 degrees C at pH 7.0. Under the same conditions, the time-dependence of inactivation is biphasic in a semi-logarithmic plot with half-lives of 10.9 min and 65.9 min. Incubation with 2,3-butanedione lowering markedly the maximal rate of ATPase activity does not modify the Km for MgATP. These data suggest that two classes of arginyl residues play essential role in the plasma membrane ATPase activity. Magnesium adenosine 5'-triphosphate (MgATP) and magnesium adenosine 5'-diphosphate (MgADP), the specific substrate and product, protect partially against enzyme inactivation by 2,3-butanedione. Free ATP or MgGTP which are not enzyme substrates do not protect. Free magnesium, another effector of enzyme activity, exhibits partial protection at magnesium concentrations up to 0.5 mM, while increased inactivation is observed at higher Mg2+ concentrations. These protections indicate either the existence of at least one reactive arginyl in the substrate binding site or a general change of enzyme conformation induced by MgATP, MgADP or free magnesium.

The arginines of cytochrome c. The reduction-binding site for 2,3-butanedione and ascorbate.

The reactions of both ferric and ferrous horse heart cytochrome c with 2,3-butanedione, pH 7.5, 0.05 M bicarbonate buffer, under a variety of solution conditions, have been examined using amino acid integrity as the primary criterion. The only observable structural alteration was the modification of both the arginyl side chains. The reaction profiles were found to be dependent upon the presence or absence of borate and ascorbate. The single-phased modification of the arginyl side chains in ferrocytochrome c in the absence of borate is rendered biphasic in the presence of borate (borate/reagent ratio of 0.04) through substantial lowering of the rate of reaction of one of the two arginyl side chains. The addition of ascorbate inhibits the reaction in a competitive manner, particularly of the arginyl side chain undergoing rapid modification in its absence. The reactivity of both arginyl side chains to reagent for the ferricytochrome was appreciably larger than for ferrocytochrome c. The addition of reagent to ferricytochrome c also reduces heme iron, which is discerned from the development of a native-like spectrum in the region 500 to 600 nm. The differences in the reactivities of the arginyl side chains to 2,3-butanedione in the two valence states of heme iron are the reflection of small, but definite, conformational differences at the two sites in the two valence states of the protein. The concurrent reduction of heme iron and the modification of the arginyl side chains localizes the reduction and the reaction site for 2,3-butanedione. The inhibition by ascorbate of the reaction of one of the two arginines also identifies the binding domain. Of the two arginines, Arg-38 is suggested to be the ascorbate-binding site.

PERTURBATION OF THE STRUCTURE OF CLOSTRIDIUM PERFRINGENS ENTEROTOXIN BY SODIUM DODECYL SULFATE, GUANIDINE HYDROCHLORIDE, pH AND TEMPERATURE

The effects of sodium dodecyl sulfate, guanidine · HCl, heat and pH on the tertiary structure of Clostridium perfringens type A enterotoxin were determined by UV difference spectroscopy and by accessibility of the amino groups to 2, 4, 6-trinitrobenzene sulfonic acid (TNBS) and the one sulfhydryl group to 5, 5′-dithiobis (2-nitrobenzoic acid) (DTNB). Biological stability of enterotoxin at several pH's at 55°C in the presence and absence of borate and dipicolinate ions was determined by the guinea pig skin test. Sodium dodecyl sulfate and heat did not unfold the molecule while treatment with >4.5 M guanidine · HCl at ≥25°C completely unfolded the molecule based on UV difference spectral changes and the accessibility of the amino groups to reaction with TNBS. Sodium dodecyl sulfate, at 0.2%, made the sulfhydryl group accessible to DTNB but did not affect the accessibility of the amino groups (7.89 ± 0.15 groups in the native molecule). Guanidine · HCl, at 6.5 M for 30 min and ≥25°C, made all 17 e-amino groups and the one α-amino group accessible to TNBS. At pH's above 8 spectral differences, in relation to the spectrum at pH 6.8, were associated primarily with ionization of the tyrosine residues while at pH's below 5.5 the spectral changes were probably a result of protonation of carboxyl groups in the vicinity of tyrosine and tryptophan residues, and of aggregation.

Pyranoside derivatives of 3-deoxyald-2-ulosonic acids

At pH 11.5 in 0.2M-sodium tetraborate solution and in the presence of Ni2+, 2-O-benzyl-D-arabinose reacts with oxaloacetic acid to give a 50–60% yield of 5-O-benzyl-3-deoxyoct-2-ulosonic acids (mixed D-gluco- and D-manno-isomers). The methyl esters of these were separated and the α-methyl glycoside of the D-manno-isomer was prepared. The conformation of the compounds was established by n.m.r. spectroscopy at 250 MHz. It was observed that esterification of the carboxy-group greatly increases the stability of the glycosidic bond of 3deoxy-D-manno-octulosonic acid while the benzyl substituent in position 5 exerts only a weak stabilising effect. 2-O-Benzyl-D-glyceraldehyde, when treated with oxaloacetic acid in the presence of Ni2+ at pH 7 in the absence of borate, yields 5-O-benzyl-3-deoxyhex-2-ulosonic acids, the predominant D-erythro-isomer being isolated as its methyl ester.

D-Serine dehydratase from Escherichia coli. Essential arginine residue at the pyridoxal 5'-phosphate binding site.

D-Serine apodehydratase from Escherichia coli is rapidly inactivated by butanedione in K+ borate buffer or by phenylglyoxal in K+ phosphate buffer at pH 8, 25 degrees. Pyridoxal-P protects against the inactivation. Modification of the apoenzyme abolishes its ability to bind the cofactor, pyridoxal-P, but the apparent Km for the substrate, D-serine, is not altered. The concentration dependence of the rate of butanedione inactivation in K+ borate buffer indicates that it is a two-step process with one butanedione bound per molecule of apoenzyme to give an inactive complex; half-maximal rate of inactivation is obtained at 37 mM butanedione. Butanedione inactivation is fully reversed following removal of excess reagent and borate. Similar studies with [14C]phenylglyoxal show that in the presence of pyridoxal-P at least 2 arginine residues may be modified without loss of activity. In the absence of pyridoxal-P modification of a single additional arginine residue results in loss of activity. Results with both inactivating reagents thus demonstrate that a critical arginine residue participates in binding of the coenzyme, pyridoxal-P. The stoichiometry of phenylglyoxal incorporation into the enzyme is different in the presence and absence of borate. Under both conditions incorporated phenylglyoxal is slowly lost on dialysis at neutral pH. A possible explanation of these effects is discussed.

Antifreeze glycoproteins from Antarctic fish. Inactivation by borate.

Antifreeze glycoprotein, which has previously been shown to be inactive in the presence of borate, migrates electrophoretically as the borate complex, presumably through formation of borate complexes with hydroxyl groups on the sugar side chains. Antifreeze glycoprotein (5 mg/ml) has been found to be completely active in the presence of 0.1 M borate at pH 7, but inactive at pH 9. A titration curve of pH versus the antifreeze activity of glycoprotein (5 mg/ml) in 0.1 M borate showed a progressive decrease in antifreeze activity as the pH was increased. Concomitant with decreases in activity were increases in binding of borate. At pH 9.0, nearly 2 mol of borate were complexed per glycotripeptide. Ultracentrifuge analyses showed similar molecular weights and laser quasi-elastic light scattering showed similar diffusions at pH 7.0 and 9.0 in borate and in the absence of borate. The binding of borate, rather than a change in conformation, is thus directly related to the loss of antifreeze activity. Alkaline borate also decreased hemagglutinating activity of Osage orange lectin and decreased the inhibition of the activity by the antifreeze glycoproteins.

Regulation of Renal Ammoniagenesis: SUBCELLULAR LOCALIZATION OF RAT KIDNEY GLUTAMINASE ISOENZYMES

Abstract Rat kidney contains two distinct glutaminase isoenzymes; one of which is phosphate-dependent, the other is phosphate-independent but is strongly activated by maleate. The phosphate-dependent glutaminase is contained within mitochondria. Its activity cofractionates with mitochondrial marker activities during differential centrifugation and on sucrose gradients using both isopycnic and sedimentation velocity techniques. Incubation of mitochondria with borate buffer results in increased phosphate-dependent glutaminase, cytochrome oxidase, and malate dehydrogenase activities, indicating that this glutaminase activity may be latent. Submitochondrial fractionation by digitonin-Lubrol treatment in the presence of borate indicated that this glutaminase isoenzyme is contained in the inner mitochondrial membrane. This conclusion was confirmed by a swell-shrink, sonication procedure carried out in the absence of borate. Only 25 to 35 % of the phosphate-independent glutaminase was associated with the mitochondrial fraction obtained by differential centrifugation; the remaining activity was pelleted by subsequent centrifugation at 40,000 x g for 30 min (heavy microsomes). The phosphate-independent glutaminase in both fractions banded during isopycnic centrifugation with a mean density (1.166) similar to that of light mitochondria. However, the results of sedimentation velocity centrifugation studies showed that this isoenzyme was contained in an organelle distinct from mitochondria. The phosphate-independent glutaminase did not fractionate with marker activities for lysosomes, microsomes, or plasma membranes during differential centrifugation or isopycnic gradient analysis and may be contained in some as yet unidentified organelle.

The electrolysis of a carbonate-borate solution with a platinum anode—II. Relation between current efficiency and perborate concentration

The current efficiency R (corrected for the chemical disproportionation of H 2O 2 in the bulk of electrolyte) of the electrolytic formation of perborate decreases with increasing concentration of H 2O 2. The factors causing this decrease were investigated. The relation between R and [H 2O 2] and the diffusion coefficient of H 2O 2 were determined under various conditions. The relation between the thickness of the Nernst diffusion layer and the rate of oxygen evolution was established. The stability of peroxocarbonate at −15°C was also examined. The slope of the linear R/[H 2O 2] curve increases with decreasing cd, with increasing pH and temperature, by replacement of Na + by K +, rotation of the anode and in absence of borate. The decrease of R with increasing [H 2O 2] is caused by two reactions, oxidation of H 2O 2 at the anode and reaction between H 2O 2 and a peroxocarbonate compound in the electrolyte.

Boron in plants: a biochemical role.

Boron, as borate, appears to have a role in partitioning metabolism between the glycolytic and pentose-shunt pathways. This effect results from the association of borate with 6-phosphogluconic acid, forming a virtual substrate that inhibits the action of 6-phosphogluconate dehydrogenase. In the absence of borate, the inhibition of the enzyme is released, and excess phenolic acids are formed. These acids also associate strongly with borate and thus develop an autocatalytic system for production of excess phenolic acids which cause necrosis of tissue and eventual death of the plant.

The enzymatic conversion of uric acid spectrophotometric analysis

The disappearance of the light absorption of uric acid in enzymatic experiments is generally not a true expression of the disappearance of uric acid. The spectral changes involved, show that at least two intermediate substances are transitorily accumulated, which cause a retardation of the disappearance of the absorption at the maximum wave-length and the occurrence of a transitory absorption at wave-lengths at which uric acid produces little or no absorption. The accumulation of the intermediate substances is very slight when borate ions are present and the pH not above 8. The reason for this is that the primary intermediate substance, which absorbs the long-waved and also the short-waved ultraviolet, is rapidly decomposed in the presence of borate. This decomposition is independent of the pH. The end products have only slight absorption and exclusively in the short-waved region. The disappearance of uric acid may therefore be followed, and the activity of uricase may be estimated, through observations of the disappearance of the absorption at the maximum wavelength of uric acid in systems with borate buffer of pH 8. The primary intermediate substance may be examined in the absence of borate and at a higher wave-length at which uric acid does not absorb. The secondary intermediate compound may be examined separately at shorter wave-lengths, when uric acid has disappeared, and when the primary substance has been excluded by the addition of borate. The absorption of the secondary substance is greater as the pH increases. Both the formation velocity and the decomposition velocity of the secondary substance is increased with an increasing pH. From a comparison of these results with the findings of Klemperer it seems probable, that the formation of allantoin is conditioned by a rapid decomposition of a secondary intermediate compound. Under conditions at which this decomposition is relatively slow the formation of other end products from the primary intermediate substance will predominate.