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PubMed2006

Structural basis of peroxide-mediated changes in human hemoglobin: a novel oxidative pathway.

Hydrogen peroxide (H(2)O(2)) triggers a redox cycle between ferric and ferryl hemoglobin (Hb) leading to the formation of a transient protein radical and a covalent hemeprotein cross-link. Addition of H(2)O(2) to highly purified human hemoglobin (HbA(0)) induced structural changes that primarily resided within beta subunits followed by the internalization of the heme moiety within alpha subunits. These modifications were observed when an equal molar concentration of H(2)O(2) was added to HbA(0) yet became more abundant with greater concentrations of H(2)O(2). Mass spectrometric and amino acid analysis revealed for the first time that betaCys-93 and betaCys-112 were oxidized extensively and irreversibly to cysteic acid when HbA(0) was treated with H(2)O(2). Oxidation of further amino acids in HbA(0) exclusive to the beta-globin chain included modification of betaTrp-15 to oxyindolyl and kynureninyl products as well as betaMet-55 to methionine sulfoxide. These findings may therefore explain the premature collapse of the beta subunits as a result of the H(2)O(2) attack. Analysis of a tryptic digest of the main reversed phase-high pressure liquid chromatography fraction revealed two alpha-peptide fragments (alpha128-alpha139) and a heme moiety with the loss of iron, cross-linked between alphaSer-138 and the porphyrin ring. The novel oxidative pathway of HbA(0) modification detailed here may explain the diverse oxidative, toxic, and potentially immunogenic effects associated with the release of hemoglobin from red blood cells during hemolytic diseases and/or when cell-free Hb is used as a blood substitute.

Blood Substitutes↗
PubMed1982

Composition of peptidoglycans in Bacteroidaceae: determination and distribution of lanthionine.

Peptidoglycans of organisms belonging to the strictly anaerobic family Bacteroidaceae were investigated for the presence of lanthionine. Different procedures for the quantitation of lanthionine were compared. Performic acid and peroxide oxidation procedures on 35S-labeled peptidoglycan from Fusobacterium nucleatum Fev1 resulted in low yields of cysteic acid (42 and 60%, respectively) and many other additional unidentified oxidation products. Lanthionine was, however, recovered in high yield (89% or more) from acid hydrolysates of unoxidized peptidoglycans. Lanthionine was found exclusively in some species of Fusobacterium, in particular F. nucleatum, F. necrophorum, F. russi, and F. gonidiaformans, for which lanthionine may be ascribed a function as a taxonomic marker. Peptidoglycans of these bacteria are thus proposed to belong to a new chemotype, assigned A1 delta. One strain of Fusobacterium, F. mortiferum VPI 0473 contained both lanthionine and diaminopimelic acid in about equal proportions. Species of F.plauti had a composition atypic of gram-negative cells. Chemotypic differences were also indicated among the species of Bacteroides investigated. Thus, some species contained lysine and not diaminopimelic acid as the major dibasic amino acid (e.g., F. asaccharolyticus). It is concluded that peptidoglycans of gram-negative organisms constitute a somewhat more heterogeneous group than hitherto assumed.

Alanine↗
PubMed1987

Chemical characterization of recombinant human leukocyte interferon A using fast atom bombardment mass spectrometry.

Proteolytic digests of biologically active fractions of recombinant human leukocyte interferon A expressed in large quantities in Escherichia coli were analyzed by fast atom bombardment mass spectrometry and high-performance liquid chromatography. The values observed in the mass spectra of digests of the major fraction of recombinant human leukocyte interferon A with trypsin and Staphylococcus aureus protease V8 accounted for 93% of the amino acid sequences of human leukocyte interferon A predicted from the nucleotide sequence of the gene encoding the protein, indicating that the major fraction of recombinant human leukocyte interferon A was expressed with the same amino acid sequence as that translated from the nucleotide sequence of the gene encoding the protein. Mass spectrometry of proteolytic digests of two minor fractions of recombinant human leukocyte interferon A and mass and amino acid analyses of their high-performance liquid chromatography fractions showed that the amino group of the N-terminal amino acid residue of interferon was in part acetylated, and the Cys-1 and Cys-98 residues were oxidized to cysteic acid or linked to glutathione. These findings suggest that amino acid residues in recombinant proteins prepared in large quantities in E. coli are modified post-translationally.

Amino Acid Sequence↗
PubMedDate not supplied

Neural changes in acute arthritis in monkeys. IV. Time-course of amino acid release into the lumbar dorsal horn.

Extracellular levels of amino acids were measured during the development of experimental arthritis in anesthetized monkeys. Levels of glutamate, aspartate, glycine, serine, glutamine, taurine, cysteic acid and asparagine were each measured in consecutive 30 min samples before, during and for several hours after injection of kaolin and carrageenan into the articular capsule of one knee. Samples were obtained via a microdialysis probe placed in the lumbar dorsal horn ipsilateral to the injected knee and assayed using HPLC with fluorescence detection. Glutamate, aspartate, glycine and serine increased transiently following intra-articular injection of inflammatory agents. During this period glutamine levels decreased. A second phase of release then occurred which included more prolonged changes in amino acid levels that were sometimes of greater magnitude than those immediately following the injection. In animals which were later observed to have depletion of SP in the dorsal horn of the inflamed side, taurine levels increased starting after the Glu, Asp and Gly had plateaued at near baseline concentrations. Thus during the first stages of joint inflammation EAAs are released into the dorsal horn, followed by increased levels of IAAs, possibly representing activation of the descending endogenous analgesia system. This phase is followed by a semiacute response consisting in part of increased extracellular levels of SP and Tau. While SP is presumably part of an ascending nociceptive transmission system, Tau could be part of a second system aimed at reducing excessive neural activity including neural transmission resulting in intense maintained pain.

Acute Disease↗
PubMed1977

Ribonuclease inhibitor from human placenta. Purification and properties.

A soluble ribonuclease inhibitor from the human placenta has been purified 4000-fold by a combination of ion exchange and affinity chromatography. The inhibitor has been isolated in 45% yield (about 2 mg/placenta) as a protein that is homogeneous by sodium dodecyl sulfate-gel electrophoresis. In common with the inhibitors of pancreatic ribonuclease from other tissues that have been studied earlier, the placental inhibitor is an acidic protein of molecular weight near 50,000; it forms a 1:1 complex with bovine pancreatic RNase A and is a noncompetitive inhibitor of the pancreatic enzyme, with a Ki of 3 X 10(-10) M. The amino acid composition of the protein has been determined. The protein contains 30 half-cystine plus cysteine residues determined as cysteic acid after performic acid oxidation. At pH 8.6 the nondenatured protein alkylated with iodoacetic acid in the presence of free thiol has 8 free sulfhydryl groups. The inhibitor is irreversibly inactivated by sulfhydryl reagents and also by removal of free thiol from solutions of the protein. Inactivation by sulfhydryl reagents causes the dissociation of the RNase - inhibitor complex into active RNase and inactive inhibitor.

Amino Acids↗
PubMed1989

Excitatory amino acids enhance dissociation of zinc from soluble protein in cytosol of rat hippocampus.

An ultra-filtration method for separating free Zn from its bound form with macromolecules was used to study the effect of excitatory amino acids on dissociation of Zn in the soluble fraction of rat hippocampus. L-Glutamate, L-aspartate and L-cysteic acid but not D-glutamate significantly increased the dissociated Zn at the concentration of 100 microM. 2-Amino-5-phosphonovalerate did not inhibit the effect of L-glutamate. Likewise, the stimulatory effect of N-methyl-DL-aspartate and quisqualate was observed at the concentration range between 1 and 100 microM. The effect of kainate was much less potent. Taurine and GABA had no stimulatory effect on the dissociation of Zn.

Amino Acids↗
PubMedDate not supplied

Hydrolysate preparation for analysis of amino acids in sorghum grains: effect of oxidative pretreatment.

Sorghum samples were either untreated or oxidized with performic acid (PA) before hydrolysis, and their amino acid contents were determined by cation exchange chromatography using an amino acid analyzer. HCl was used to destroy excess PA. Oxidative pretreatment of the samples resulted in increased yields of Cys (as cysteic acid), Met (as Met dioxide), and His, destroyed Tyr and Phe, and resulted in the appearance of an extraneous peak which most likely consisted of halogenation by-products (HBP) of Tyr and Phe. The destruction of Tyr and Phe occurred despite the presence of phenol, a halogen scavenger, in both the PA and hydrolysis reagents. The higher His values observed in all oxidized samples most likely resulted from the co-elution of His with Tyr and Phe HBP. It was concluded that the complete (except Trp) amino acid content of a feedstuff cannot be accurately determined from only one oxidized hydrolysate preparation by using this particular procedure.

Amino Acids↗
PubMed1975

Purification and properties of rat liver adenine phosphoribosyltransferase.

The adenine phosphoribosyltransferase (AMP: pyrophosphate phosphoribosyltransferase, EC 2.4.2.7) of rat liver was purified to a specific activity of 1.1 mumol of AMP formed per min per mg. The enzyme activity is associated with an apparently homogenous protein as shown by isoelectrofocusing, acrylamide gel electrophoresis, and N-terminal amino acids analysis (phenylalanine). The molecular weight of the enzyme was estimated to be approx. 20 000 by acrylamide gel electrophoresis in the presence of sodium dodecylsulfate and by sucrose density gradient zone sedimentation. The rat liver enzyme exhibited initial burst synthesis of AMP when 1-pyrophosphorylribose 5-phosphate was added. The 1-pyrophosphorylribose 5-phosphate initial-burst activity copurifies with the adenine phosphoribosyltransferase activity. A PH optimum of 10.0 was demonstrable for the adenine phosphoribosyltransferase. The initial-burst and steady-state phases of AMP synthesis catalyzed by highly purified rat liver adenine phosphoribosyltransferase have been partially characterized by the use of ligands which bind to sulfhydryl groups. Studies utilizing p-chloromercuribenzoate and HgCl2 as inhibitors of AMP sulfhydryl during the initial-burst and steady-state phases have revealed that sulfhydryl groups with different rates of ligand binding are present in the enzyme. The initial-burst phase was thereby delineated from the steady-state phase by use of these mercurial ligands. This delineation was also accomplished by titration with the Mg-2+ chelator, EDTA. The inhibitory effects of mercurials and EDTA were reversed by beta-mercaptoethanol and excess Mg-2+, respectively. Quantitative binding studies with 5,5'-dithiobis(2-nitrobenzoic acid) and p-chloromercuribenzoate yielded values of 3.65 and 3.6 mol of sulfhydryl per mol of enzyme, respectively. 3.3 mol of cysteic acid per mol of performic acid-oxidized enzyme were found by amino acid analysis.

Adenine Phosphoribosyltransferase↗
PubMed1972

Covalent structure of bovine neurophysin-II: localization of the disulfide bonds.

The completed amino-acid sequence of bovine neurophysin-II, a major neurohypophyseal hormone-binding protein in the hypothalamo-neurohypophyseal complex of cows, set the stage for the localization of the disulfide bonds of this sulfur-rich molecule. Neurophysin-II was digested with subtilisin or a pepsin-trypsin mixture. The resulting peptides were subjected to first-dimensional electrophoresis at pH 6.5, oxidized with performic acid, and subjected to second-dimensional electrophoresis under identical conditions as the first-dimensional separation, but in a perpendicular direction. Cysteic acid peptides were eluted (several after additional electrophoretic purification at pH 3.5) for amino-acid composition and NH(2)- and COOH-terminal analyses. Our assignment of the seven disulfide bridges present in neurophysin-II is as follows: Cys(10)-Cys(93); Cys(13)-Cys(95); Cys(21)-Cys(27); Cys(28)-Cys(44); Cys(54)-Cys(61); Cys(67)-Cys(73); Cys(74)-Cys(79). The assignment of disulfide bridges associated with Cys(27) and Cys(28) is tentative as it is derived from evolutionary consideration. The high disulfide content reduces drastically the allowed number of biofunctional conformers of neurophysin-II. It is suggested that neurophysin-II possesses a globular topography with minimal alpha-helix structure.

Amino Acid Sequence↗
PubMed2005

High efficiency micellar electrokinetic chromatography of hydrophobic analytes on poly(dimethylsiloxane) microchips.

This paper describes a simple method for the effective and rapid separation of hydrophobic molecules on polydimethylsiloxane (PDMS) microfluidic devices using Micellar Electrokinetic Chromatography (MEKC). For these separations the addition of sodium dodecyl sulfate (SDS) served two critical roles - it provided a dynamic coating on the channel wall surfaces and formed a pseudo-stationary chromatographic phase. The SDS coating generated an EOF of 7.1 x 10(-4) cm(2) V(-1) s(-1) (1.6% relative standard deviation (RSD), n = 5), and eliminated the absorption of Rhodamine B into the bulk PDMS. High efficiency separations of Rhodamine B, TAMRA (6-carboxytetramethylrhodamine, succinimidyl ester) labeled amino acids (AA), BODIPY FL CASE (N-(4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-propionyl)cysteic acid, succinimidyl ester) labeled AA's, and AlexaFluor 488 labeled Escherichia coli bacterial homogenates on PDMS chips were performed using this method. Separations of Rhodamine B and TAMRA labeled AA's using 25 mM SDS, 20% acetonitrile, and 10 mM sodium tetraborate generated efficiencies > 100,000 plates (N) or 3.3 x 10(6) N m(-1) in <25 s with run-to-run migration time reproducibilities <1% RSD over 3 h. Microchips with 30 cm long serpentine separation channels were used to separate 17 BODIPY FL CASE labeled AA's yielding efficiencies of up to 837,000 plates or 3.0 x 10(6) N m(-1). Homogenates of E. coli yielded approximately 30 resolved peaks with separation efficiencies of up to 600,000 plates or 2.4 x 10(6) N m(-1) and run-to-run migration time reproducibilities of <1% RSD over 3 h.

Amino Acids↗
PubMedDate not supplied

Complete amino acid analysis in hydrolysates of foods and feces by liquid chromatography of precolumn phenylisothiocyanate derivatives.

The amino acid analysis method using precolumn phenylisothiocyanate (PITC) derivatization and liquid chromatography was modified for accurate determination of methionine (as methionine sulfone), cysteine/cystine (as cysteic acid), and all other amino acids, except tryptophan, in hydrolyzed samples of foods and feces. A simple liquid chromatographic method (requiring no derivatization) for the determination of tryptophan in alkaline hydrolysates of foods and feces was also developed. Separation of all amino acids by liquid chromatography was completed in 12 min compared with 60-90 min by ion-exchange chromatography. Variation expressed as coefficients of variation (CV) for the determination of most amino acids in the food and feces samples was not more than 4%, which compared favorably with the reproducibility of ion-exchange methods. Data for amino acids and recoveries of amino acid nitrogen obtained by liquid chromatographic methods were also similar to those obtained by conventional ion-exchange procedures.

Amino Acids↗
PubMed2000

Methylene blue photosensitized oxidation of cysteine sulfinic acid and other sulfinates: the involvement of singlet oxygen and the azide paradox.

The methylene blue photosensitized oxidation of cysteine sulfinic acid is investigated. Enhancement of the oxygen consumption rate in deuterium oxide suggests the involvement of singlet oxygen ((1)O(2)) in oxidation. Addition of the (1)O(2) quencher azide produced an unusual enhancement of the oxidation rate of all the sulfinates assayed. It is assumed that azide works as a one-electron carrier between (1)O(2) and the sulfur compounds. Analyses of the products indicate that the photochemical oxidation of cysteine sulfinic acid proceeds through two simultaneous mechanisms. The Type II (singlet oxygen) mechanism is responsible for oxidation of the sulfinic group to the sulfonic group with production of cysteic acid, stable to the photooxidation system, whereas the Type I (electron transfer) mechanism is involved in the degradation of cysteine sulfinic acid to acetaldehyde. Other products detected were ammonia, sulfate, and hydrogen peroxide which account for the degradation of cysteine sulfinic acid and for the excess of oxygen consumption detected during the oxidative reaction.

Aerobiosis↗
PubMed1989

Hydrolysis of proteins and peptides in a hermetically sealed microcapillary tube: high recovery of labile amino acids.

A method for the hydrolysis of peptides and proteins in a hermetically sealed microcapillary tube has been developed. The method is based on the concept that oxidative degradation of labile amino acids during acid hydrolysis of proteins and peptides at high temperature can be reduced to a minimum by limiting the ratio of air to liquid (v/v, less than 1:10) in a microcapillary tube. Furthermore, the physical constraints imposed by the capillary tube will restrict the exposure of the protein solution to air at a very limited area at the meniscus of the liquid. This method eliminates the necessity of time-consuming sealing under vacuum and/or flushing with nitrogen to remove oxygen in the hydrolysis tube. High recovery of labile amino acids can be obtained in a reproducible manner. Because of the simplicity and high reproducibility of the method described, it could be the method of choice for the hydrolysis of protein and peptide intended for quantitative amino acid analysis. Performic acid oxidation is performed at 50 degrees C for 10 min instead of 4 to 20 h at 0 degrees C to achieve an equally good yield of cysteic acid and methionine sulfone from peptides and proteins.

Amino Acids↗
PubMed1982

Characterization of glutamic acid decarboxylase activity in cerebral blood vessels.

Glutamic acid decarboxylase activity associated with cerebral blood vessels appears to be part of a specific cerebrovascular system involving gamma-aminobutyric acid. This activity was characterized kinetically and pharmacologically and compared with that in brain and several nonneuronal tissues. Formation of gamma-aminobutyric acid from [14C]glutamate was measured in a soluble extract of pia-arachnoid blood vessels isolated from bovine brain. The vascular activity was like brain glutamate decarboxylase in that it required pyridoxal phosphate, was completely inhibited by aminooxyacetic acid, and had a similar affinity for glutamate. Cerebrovascular decarboxylase activity differed, however, from brain decarboxylase in that it was less sensitive to sulfhydryl reagents, was stimulated by 3-mercaptopropionic and cysteic acids, and was competitively inhibited by cysteine sulfinic acid. The glutamate decarboxylase activity of the cerebral vessels was similar to that in renal cortex and mesenteric blood vessels in its responses to sulfhydryl reagents and 3-mercaptopropionic acid. These findings are consistent with previous suggestions of a nonneuronal form of the enzyme and offer the possibility that synthesis of gamma-aminobutyric acid in cerebral blood vessels can be manipulated independently from that in neuronal tissue.

Animals↗
PubMed1976

Attempts at inhibition of autooxidation of catecholamines in vitro.

The authors attempted to inhibit autooxidation of catecholamines in vitro by means of sulphur-containing amino-acids, monosaccharides, and aminobutyric acids. The SH group-containing amino-acids were found to suppress autooxidation of catecholamines passing from a chloroform-methanol solution (2:1) to water or buffer solutions. A similar though less pronounced property was manifested by cysteic acid. Likewise glucose, fructose and galactose blocked the reaction. Among aminobutyric acids only gamma-aminobutyric acid inhibited autooxidation of amines. However, despite positive results obtained, these experiments cannot be utilized in studies on reduction of Nitro-BT, as no reduction of Nitro-BT occured in the solutions in which catecholamine autooxidation was brought to a stop.

Amino Acids↗
PubMed1988

Colocalization of taurine- and cysteine sulfinic acid decarboxylase-like immunoreactivity in the cerebellum of the rat with monoclonal antibodies against taurine.

Two monoclonal antibodies against fixative-modified taurine, Tau1 and Tau2, were produced, characterized, and used in the present study to analyze the distribution of taurine in the cerebellum of the rat. In addition, immunohistochemical colocalization experiments were performed to determine whether cerebellar neurons contain both taurine and its synthesizing enzyme, cysteine sulfinic acid decarboxylase (CSADC). In ELISAs, both Tau1 and Tau2 displayed high affinities for taurine conjugated to various carrier proteins and possessed some cross-reactivity for other amino acids which are present in lower concentrations in the brain than taurine. Tau2 was found to recognize only taurine and hypotaurine when paraformaldehyde was used to fix the amino acids to carrier proteins. With the use of glutaraldehyde fixation, Tau1 cross-reacted with conjugates of beta-alanine and hypotaurine and Tau2 cross-reacted strongly with conjugates of cysteic acid and hypotaurine and weakly with cysteine sulfinic acid. Despite different cross-reactivities, Tau1 and Tau2 exhibited almost identical patterns of neuronal staining in bands of Purkinje cells in the cerebellum. Staining of Purkinje cell dendrites was more prominent than staining of the soma. Light immunoreactivity was present in Golgi, stellate, and basket cells. A scattered population of granule cells displayed taurine-like immunoreactivity at the electron microscopic level. Immunostaining was identified in some terminals in the Purkinje cell layer and in a limited number of mossy fibers. Tau2-like immunoreactivity was colocalized with CSADC-like immunoreactivity in the cerebellar neurons described above. These immunoreactive cells may represent a subpopulation of neurons that contain a higher concentration of taurine than neighboring cells due to their ability to synthesize taurine. The intense immunoreactive staining of Purkinje cell dendrites provides support for the hypothesis that calcium-dependent release of taurine in the cerebellum may originate primarily from dendritic rather than synaptic processes and suggests a neuromodulator role for taurine in the cerebellum.

Animals↗
PubMed1972

Biosynthesis of vasopressin in vitro and ultrastructure of a bronchogenic carcinoma. Patient with the syndrome of inappropriate secretion of antidiuretic hormone.

Tumors from patients with the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) have been found to contain large amounts of the antidiuretic hormone vasopressin. A lung tumor from a patient with hyponatremia most likely due to SIADH was removed at surgery and found to contain 23.5 mU vasopressin/g wet weight by radioimmunoassay Slices of this tumor were incubated with phenylalanine-(3)H. Arginine vasopressin-(3)H was purified from the incubate by Sephadex G-25 column chromatography in two different systems, performic acid oxidation, and gradient elution column chromatography with diethylaminoethyl Sephadex. As oxidation of vasopressin results in drastic conformational change with breaking of the ring of the cyclic polypeptide and addition of two cysteic acid residues per molecule, the radioactive material which eluted coincident with vasopressin both before and after this procedure was considered to be arginine vasopressin-(3)H. To our knowledge this is the first demonstration of in vitro biosynthesis of vasopressin by a tumor from a patient with SIADH.Ultrastructurally, the bronchogenic carcinoma was composed of small undifferentiated and granulated cells. The granulated neoplastic cells had well developed organelles (endoplasmic reticulum, free ribosomes) concerned with protein synthesis. Secretion granules present in the tumor cells were small, surrounded by a limiting membrane, and resembled those reported in polypeptide hormone-secreting cells.

Aged↗