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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An extracellular proteolytic enzyme of Legionella pneumophila was purified by sequential batch separation with DEAE-cellulose, hydrophobic interaction chromatography with octyl-Sepharose, and ion-exchange chromatography with DEAE-Bio-Gel A (Bio-Rad Laboratories, Richmond, Calif.). The resulting protease preparation was determined to be homogeneous by polyacrylamide gel electrophoresis in the presence and absence of sodium dodecyl sulfate. Although free of contaminating proteins, the purified protease separated into two antigenically indistinguishable proteins both of which possessed proteolytic activity. The apparent masses of the proteins were 38 and 40 kilodaltons (kDa) as determined by polyacrylamide gel electrophoresis in sodium dodecyl sulfate, whereas gel filtration chromatography revealed a single mass of 34 kDa. Immunoblot analysis indicated that the 38-kDa protein probably originated from the 40-kDa protein during purification. The isoelectric points of the two protease species were 4.20 and 4.42. Enzyme activity, which was optimum between pH 5.5 and 7.5, was inhibited by various metal chelators; however, no effect was observed after treatment with phenylmethylsulfonyl fluoride, chymostatin, trypsin inhibitor, or dithiothreitol. Enzyme activity inhibited by metal chelators was restored upon the addition of various metal ions, including Zn2+, Fe2+, Mn2+, Cu2+, and Fe3+, but was not restored by Mg2+ or Ca2+. Atomic absorption analysis of the purified protease revealed a single gram-atom of zinc per mole of enzyme. Our findings indicate that the L. pneumophila protease resembles neutral zinc-containing metalloproteases similar to those found in other bacterial species.
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PMID:Purification and characterization of an extracellular protease of Legionella pneumophila. 351 31

By gel filtration and titration on DEAE-cellulose filters we show that Escherichia coli tryptophanyl-tRNA synthetase forms tryptophanyl adenylate as an initial reaction product when the enzyme is mixed with ATP-Mg and tryptophan. This reaction precedes the synthesis of the tryptophanyl-ATP ester known to be formed by this enzyme. The stoichiometry of tryptophanyl adenylate synthesis is 2 mol per mole of dimeric enzyme. When this reaction is studied either by the stopped-flow method, by the fluorescence changes of the enzyme, or by radioactive ATP depletion, three successive chemical processes are identified. The first two processes correspond to the synthesis of the two adenylates, at very different rates. The rate constants of tryptophanyl adenylate synthesis are respectively 146 +/- 17 s-1 and 3.3 +/- 0.9 s-1. The third process is the synthesis of tryptophanyl-ATP, the rate constant of which is 0.025 s-1. The Michaelis constants for ATP and for tryptophan in the activation reaction are respectively 179 +/- 35 microM and 23.9 +/- 7.9 microM, for the fast site, and 116 +/- 45 microM and 3.7 +/- 2.2 microM, for the slow site. No synergy between ATP and tryptophan can be evidenced. The data are interpreted as showing positive cooperativity between the subunits associated with conformational changes evidenced by fluorometric methods. The pyrophosphorolysis of tryptophanyl adenylate presents a Michaelian behavior for both sites, and the rate constant of the reverse reaction is 360 +/- 10 s-1 with a binding constant of 196 +/- 12 microM for inorganic pyrophosphate (PPi).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Tryptophanyl adenylate formation by tryptophanyl-tRNA synthetase from Escherichia coli. 351 15

Post-mortem human vitreous samples (liquid and gel) of comparable intrinsic viscosity values (n approximately equal to 3000 cc/g) were chromatographed on DEAE-Sephacel columns at 4 degrees C using a linear salt gradient ranging from 0----0.4 M NaCl. All samples examined produced numerous discrete hyaluronic acid (HA) fractions. The HA fractions from liquid vitreous were eluted at lower salt concentrations than those from gel vitreous. Several HA fractions from vitreous analyzed by circular dichroism (CD) displayed CD minima at 210 nm, with an ellipticity value of 14 to 16 X 10(3) deg X cm2d mole-1. However, all HA fractions from liquid vitreous showed lower ellipticity values and a weak positive signal above 240 nm. This signal was absent in HA fractions from gel vitreous. Results suggest that subtle but definite conformational differences involving carboxylic groups exist between gel and liquid vitreous hyaluronate.
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PMID:Conformational differences between hyaluronates of gel and liquid human vitreous: fractionation and circular dichroism studies. 358 66

Glutathione peroxidase (GSHPx), (glutathione:H2O2 oxidoreductase, EC 1.11.1.9) was purified to homogeneity from human plasma. This resulted in a 6800-fold purification of the enzyme with a 2.8% yield. The purification process involved ammonium sulfate fractionation, DEAE-cellulose batch and column chromatographies, hydroxyapatite, and Sephadex G-200 and DEAE-Sephadex A-25 chromatographies. The major peak on DEAE-Sephadex A-25 column chromatography was found to be homogeneous on polyacrylamide gel electrophoresis in the presence or absence of sodium dodecyl sulfate (SDS). Relative mobility in nondenaturing polyacrylamide gel electrophoresis at pH 8.2 was 0.5 for the purified enzyme as detected by both protein staining and enzyme activity compared with 0.38 for erythrocyte GSHPx. The molecular weight of the plasma enzyme as determined by gel filtration was found to be approximately 100,000. SDS-gel electrophoresis of the plasma enzyme gave a subunit molecular weight of approximately 23,000. This suggests that the plasma enzyme exists as a tetramer in its native state, similar to that seen for the erythrocyte enzyme, but with slightly different mobility on SDS-gel electrophoresis. Plasma GSHPx, like the erythrocyte enzyme, was found to contain approximately four atoms of selenium per mole of protein. Utilizing iodinated concanavalin A, it was found that plasma GSHPx, but not the erythrocyte GSPx, is a glycoprotein. Purified plasma enzyme catalyzes both the reduction of tertiary butyl hydroperoxide and hydrogen peroxide. The apparent Km of plasma GSHPx for GSH is 5.3 mM and for tertiary butyl hydroperoxide it is 0.57 mM. Copper, mercury, and zinc strongly inhibit the enzyme activity of plasma GSHPx. Rabbit antibodies directed against the human erythrocyte GSHPx do not precipitate the enzyme activity of the purified plasma enzyme. Radioimmunoassay utilizing erythrocyte GSHPx and anti-erythrocyte GSHPx antibodies showed that less than 0.13% of the antigenically detectable protein is found in the purified GSHPx from plasma.
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PMID:Purification and characterization of human plasma glutathione peroxidase: a selenoglycoprotein distinct from the known cellular enzyme. 361 51

Human plasma glutathione peroxidase (GPx) was purified to homogeneity by ammonium sulfate fractionation, gel filtration on Sephadex G-150, chromatography on DEAE Sephacel, chromatofocusing with polybuffer, and gel filtration with Sephadex G-75. This isolation resulted in about 5,400-fold purification of the enzyme with a 32% yield in enzyme activity. The final preparation had a specific activity of about 28 units (mmoles NADPH oxidized) per milligram of protein. Determination of selenium on the purified enzyme revealed a content of 3.8 g atoms per mole GPx. Gel electrophoresis using SDS with standard proteins revealed a molecular weight of about 23,000 for the subunits, which would indicate a molecular weight of about 92,000 for the native enzyme. Amino acid analyses of the purified GPx indicated aspartate, glutamate, proline, glycine, alanine, and leucine as the predominant amino acids and cysteine, methionine, tryptophan, and histidine as the minor amino acids.
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PMID:Properties of glutathione peroxidase isolated from human plasma. 366 26

Highly purified 4-aminobutyrate aminotransferase from pig brain is susceptible to phosphorylation by the purified cAMP-dependent protein kinase catalytic subunit. Up to 0.7 moles of phosphate from ATP-(gamma)-32P can be incorporated per mole of dimeric holoenzyme. Maximum phosphorylation was observed within about 90 minutes at 30 degrees C. Despite the extensive degree of phosphorylation observed, no kinetic property of the enzyme was perceptibly altered. Removal of cofactor had no detectable impact on the extent of phosphorylation but thermal inactivation of the enzyme increased and mild reduction with sodium borohydride decreased the phosphorylatability of the aminotransferase. It was possible to separate the enzyme into phospho and dephospho forms by the use of DEAE chromatography. Validation that the two fractions represented genuine aminotransferase was obtained by proteolytic peptide mapping. The phospho form of the enzyme was found to possess little or no aminotransferase activity while that of the dephospho form exhibited higher specific activity than the purified enzyme prior to phosphorylation. Furthermore, the dephospho form of the enzyme could not be detectably phosphorylated by reincubation with the kinase following DEAE chromatography unless it was subjected to thermal inactivation. The stoichiometry of phosphorylation of the fraction containing 32P from DEAE chromatography was approximately 1 mole/mole of dimer. These results suggest that the substrate for phosphorylation by the kinase is a form of the aminotransferase which is somehow inactivated during routine purification even when extensive precautions are taken to maximally preserve catalytic activity.
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PMID:In vitro phosphorylation of 4-aminobutyrate aminotransferase by cAMP dependent protein kinase. 370 Jul 75

Inducible cadmium-binding proteins (Cd-BP) in the mussel, Mytilus edulis, were resolved into two molecular weight components, designated Cd-BP10 and Cd-BP20, by gel-permeation chromatography on Sephadex G-75. Each of these two molecular weight components were further resolved into four subcomponents by DEAE-ion-exchange chromatography. All eight subcomponents bound cadmium and exhibited significant UV absorption at 254 nm and little absorption at 280 nm. Each subcomponent was purified and subjected to amino acid composition analysis. Two classes were identified, one having higher cysteine (23.9-26.6 mole-%) and lower glutamic acid contents compared to the other class (11.6-18.2 mole-% cysteine). All subcomponents have a relatively high glycine content (approximately 15 mole-%) relative to mammalian metallothioneins (approximately 8 mole-%). Although the Cd-BP20 have apparent molecular weights almost twice the Cd-BP10, the exact molecular relationship between these binding proteins is not known.
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PMID:Cadmium-binding proteins in the mussel, Mytilus edulis. 370 63

The penicillinase mediated by the R factor R1 in Escherichia coli has been purified and characterized. The purification procedure contained the following three steps: spheroplast formation, chromatography of the spheroplast supernatant fluid on DEAE cellulose, and preparative polyacrylamide-gel electrophoresis. The protein obtained gave only one band in analytical polyacrylamide-gel electrophoresis. To obtain milligram quantities of the enzyme, gel filtration on Sephadex G75 was run before the last step in the purification. By gel filtration on Sephadex G75, the molecular weight was estimated as 22,000. The pH optimum, tested in universal buffer, was 7.0. The turnover numbers for benzylpenicillin, d-ampicillin, and 6-aminopenicillanic acid were 4.2 x 10(4), 6.3 x 10(4), and 2.2 x 10(4) moles of substrate hydrolyzed per min by 1 mole of enzyme, whereas the Michaelis constants were 100, 160, and 440 mum, respectively. Cephalosporins were much poorer substrates for the R1 penicillinase than were the penicillins. The turnover number for cephalosporin C, cephaloridine, and 7-amino-cephalosporanic acid were 2.4 x 10(3), 5 x 10(2), and less than 2 x 10(2), respectively. These properties show that the R1 penicillinase is quite different from the chromosomally mediated penicillinase of E. coli (11). However, the R1 enzyme resembles another R-factor penicillinase previously purified by Richmond and Datta.
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PMID:Resistance of Escherichia coli to penicillins. VII. Purification and characterization of a penicillinase mediated by the R factor R1. 490 36

Partially and highly purified sheep LH-releasing factor (LRF) induced secretion of LH during incubations of anterior pituitary slices from ovariectomized ewes treated vaginally or by subcutaneous injection with fluorogestone acetate. The incubation medium contained Krebs-Ringer bicarbonate buffer with glucose, amino acids, mannose, galactose, fucose, glucosamine, galactosamine, sialic acid, calf serum, penicillin, and streptomycin. First, the optimum effect of a dose of 45 mg fluorogestone daily for 12 days before slaughter was demonstrated. These tissues yielded about 2-6 mcg LH per mg tissue in 2 hours. A dose curve of LRF showed 4.7 mcg per mg tissue was optimal, and this dose was adjusted for the purity of the LRF used in subsequent experiments. Added LH, 15.5 mcg highly purified, did not lessen LH production. LH production was fairly constant for 4-5 hours, if the medium were not changed, but increased for up to 7 hours if the medium were renewed. After incubation with labeled amino acids or proline, LH was purified 26-fold over other proteins by ammonium sulfate fractionation DEAE-cellulose chromatography, and Sephadex gel filtration. This LH was biologically active by radioimmunoassay and by the ovary ascorbic acid depletion assay, and of high specific activity, 2.2 Ci per mole LH.
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PMID:[In vitro action of hypothalamic luteinizing hormone releasing factor (IRF) on lamb anterior pituitary. I. Kinetics of excretion of luteinizing hormone (LH)]. 493 8

Gangliosides were isolated from human, bovine, and rabbit plasma and were quantified by gas-liquid chromatography. Purification was achieved by sequential use of partitioning in solvents, DEAE-Sephadex chromatography, base treatment, and silicic acid chromatography. Human and bovine plasma yielded slightly more than 1 micro mole of lipid-bound sialic acid/100 ml; for rabbit plasma the value was 0.28 micro mole/100 ml. The total bovine plasma ganglioside fraction contained equal amounts of N-acetylneuraminic and N-glycolylneuraminic acids, rabbit plasma gangliosides had about 1% of the latter, and the human plasma sample contained only the former. Thin-layer chromatography revealed important differences among the plasmas from the three species, but all possessed hematosides and hexosamine-containing gangliosides. The approximate ratios of these two categories, based on sialic acid content, were (hematosides: hexosamine-type): human, 2:1; rabbit, 3:2; and bovine, 2:3. The fatty acid compositions of both categories were characteristic of extraneural gangliosides and included six major acids: palmitic, stearic, behenic, tricosanoic, lignoceric, and nervonic. The major long-chain base in each sample was sphingosine, while only a trace of the C(20) isomer was detected.
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PMID:Gangliosides of human, bovine, and rabbit plasma. 507 12


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