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

Isolated purified contractile tail sheaths of bacteriophage T2L were analyzed for their carboxyl terminal amino acids by carboxypeptidase treatment and hydrazinolysis. Glycine and serine were identified as the only two carboxyl end groups. Using corrections for the yields of these two amino acids upon hydrazinolysis, we calculated that there are 154 (+/-30) moles of C-terminal glycine and 130 (+/-45) moles of C-terminal serine per mole of sheath. It appears likely that sheaths contain two types of polypeptide chains in equal numbers, probably 144 of each. The relation of these two components to the mechanism of sheath contraction is discussed.
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PMID:Number of polypeptide components in bacteriophage T2L contractile sheaths. 574 39

A colorimetric assay was developed for studying the kinetics of iron oxidation with whole cells of the chemoautotroph, Ferrobacillus ferrooxidans. The assay was more advantageous than the conventional method of Warburg manometry because of its simplicity, rapidity, and the small amount of cells required. The assay measured Fe(3+) as a chloride complex which absorbs at 410 nm. Kinetic analysis showed the apparent K(m) for iron oxidation to be 5.4 x 10(-3)m in an unbuffered system and 2.2 x 10(-3)m in the presence of beta-alanine-SO(4) (2-) buffer. Glycine and beta-alanine buffers were used in the measurement of the pH optimum for iron oxidation; the optimum ranged from 2.5 to 3.8. The effect of pH was primarily on the V(max) while the K(m) remained constant. Added SO(4) (2-) was found to stimulate iron oxidation by increasing the V(max) of iron oxidation by whole cells, but it did not affect the K(m). Results of assays of iron oxidation in systems containing various mole percentages of SO(4) (2-) and Cl(-) indicated that Cl(-) did not inhibit iron oxidation but that SO(4) (2-) was required. Sulfate could be partially replaced by HPO(4) (2-) and HAsO(4) (2-) but not by BO(3) (-), MoO(4) (2-), NO(3) (-), or Cl(-); formate and MoO(4) (2-) inhibited iron oxidation.
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PMID:Kinetic studies of iron oxidation by whole cells of Ferrobacillus ferrooxidans. 580 80

The homopolymer of N-(2-hydroxypropyl)methacrylamide (HPMA) and copolymers of HPMA differing in oligopeptide side chains (-Gly-Gly-OH; -Acap-Phe-OH; -Acap-Leu-HMDA and -Gly-Phe-Tyr-OH) or in their content (1%, 3.5% and 8.4% mole of -Gly-Gly-OH side chains) were investigated with respect to their ability to induce antibody formation and mitogenic reaction in inbred strains of mice. The dependence on the antigen dose, on composition of the side chain and on the genetic background of the immunized organism was defined. It was demonstrated that the specificity of the antibody formed is predominantly directed against oligopeptide side chains, though some part of the antibody is also produced against hydroxypropyl chains. Neither the homopolymer nor the copolymers behave in the tissue culture as mitogens.
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PMID:Effect of the chemical structure of N-(2-hydroxypropyl)methacrylamide copolymers on their ability to induce antibody formation in inbred strains of mice. 673 15

Poly(His-Asp-Ser-Gly) was synthesized from the fully protected tetrapeptide active ester hydrochloride, which was prepared by stepwise coupling, using pentachlorophenyl ester and mixed anhydride methods. Complete deprotection of the protected tetrapeptide polymer was achieved by using 90% trifluoroacetic acid. The free polymer was dialyzed for 24 hr using a membrane (which retains molecules with molecular weights greater than 5000). The catalytic activity was determined by studying the hydrolysis of p-nitrophenyl acetate in 0.2 M phosphate buffer (pH 7.4) at 37 degrees. The catalytic coefficient of the dialyzed polymer was found to be 138 liters/mole/min.
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PMID:Synthesis and catalytic activity of poly-L-histidyl-L-aspartyl-L-seryl-glycine. 715 87

Amino acid analysis of oxidized or reduced and carboxymethylated beta-glucuronidase have shown the presence of 24 cysteic acid or S-carboxymethylcysteine residues respectively per mole of the tetrameric enzyme. Titration of sulfhydryl groups gave eight cysteine residues, and by difference 16 half-cystine residues per mole. Six peptides containing radiolabelled cysteine residues were isolated from pepsin and chymotrypsin digest of reduced and S-carboxymethylated beta-glucuronidase by ion-exchange chromatography or gel filtration, followed by paper ionophoresis and paper chromatography. The peptides were analysed for amino acids and sequenced by the dansyl-Edman procedure. Peptides containing cysteic acid were selectively recovered from thermolysin digests of performic acid-oxidized glucuronidase. The amino acid sequences confirmed that there were only six different peptide sequences containing either cysteine or half-cystine residues in the tetrameric enzyme, supporting the presence of four identical subunits. These sequences wer: (A)-Val-Asx-Val-Ile-Cys-Val-Asx-Ser-Tyr- (B)-Gly-Asx-Leu-Cys-Ser-Gly- (C)-Phe-Val-Val-Ile-Asx-Glx-Cys-Pro-Gly-Val-Gly- (D)-Val-Val-Cys-Leu- (E)-Gln-Ser-Gly-Cys-Leu-Val-Lys-Gly-Tyr- (F)-Cys-Asp-Arg-Tyr-Gly-Ile-Val-Val-.
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PMID:Amino acid sequences containing cysteine or half-cystine residues in beta-glucuronidase. 721 58

1. In the goldfish retina, uptake of exogenous [3H]glycine follows Michaelis--Menten kinetics with increasing concentrations of glycine. This uptake can be explained kinetically by the presence of two independent affinity systems: a 'high-affinity' mechanism with an apparent Km(H) of 8.1 microM and a Vmax(H) of 9.12 p-moles/min. mg protein, and a 'low-affinity' mechanism with an apparent Km(L) of 0.63 mM and a Vmax(L) of 430 p-mole/min . mg protein. 2. The high-affinity mechanism, and probably also the low-affinity mechanism, is temperature- and Na+-dependent. 3. The low-affinity mechanism for glycine uptake is not affected by 5 mM-isoleucine, methionine and valine in the medium. However, it is inhibited more than 90% by 5 mM-alanine, proline and serine in the medium. This result indicates that the low-affinity transport for glycine may go through system A of the neutral amino acid transport system which is present in most tissues to transport glycine and certain neutral amino acids for metabolic purposes. 4. The high-affinity mechanism for glycine uptake is, however, not affected by the presence of up to 100-fold excess of all amino acids examined. 5. Autoradiographic studies show that at least one type of amacrine cell and one type of probable interplexiform cell take up [3H]glycine both in the presence and absence of 5 mM-alanaine, proline and serine, indicating that these neurones possess the high-affinity mechanism for glycine uptake. 6. [3H]Glycine accumulated in the retina can be released by increasing the external K+ concentration. This release is probably Ca2+-dependent since it is blocked by 10 mM-Co2+ in the medium. Additionally, autoradiographic studies show that [3H]glycine taken up by the glycine-accumulating neurones can also be released by Ca2+-dependent, K+-depolarization of the retina.
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PMID:The uptake and release of [3H]glycine in the goldfish retina. 723 15

Little is known about the amino acid (AA) biosynthetic capacity and requirements of premature infants. This study assessed the synthesis of seven biochemically nonessential AA from a universal precursor, glucose, in stable, parenterally fed, premature neonates. Seven infants (six boys, one girl) were studied at a mean age of 6.3 +/- 0.6 (SEM) days; mean gestational age was 29.7 +/- 1.3 (SEM) weeks, and mean birth weight was 1,222.8 +/- 176.5 (SEM) grams. All infants were parenterally fed a mixture of 7.5% to 12.5% dextrose and 2.2% Trophamine, with or without lipid. Mean caloric intake was 93 +/- 8.4 (SEM) kcal/kg/d, and total AA intake was standardized at 2.86 g/kg/d AA, plus supplemental cysteine (30 mg/g AA/d). Each infant received a 4-hour continuous, unprimed intravenous infusion of a stable isotope tracer of D(-)[U13C] glucose (200 mg/kg). Blood samples were obtained before and at the end of the infusion. Conversion of the glucose tracer into seven biochemically nonessential AA (cysteine [Cys], proline [Pro], aspartate [Asp], serine [Ser], glutamate [Glu], alanine [Ala], and glycine [Gly]) was assessed by measuring their isotopic enrichment in plasma, using gas chromatography/mass spectrometry (GC/MS), and expressed as mole percent excess (MPE) (mean +/- SEM). The isotopic enrichment of plasma glucose was also measured using GC/MS. Free plasma AA concentrations (mean +/- SD) were measured using an automated amino acid analyzer. Mean MPE for M + 1, M + 2 and M + 3 Cys, and for M + 1 and M + 3 Pro were not significantly different from 0; M + 2 Pro barely achieved statistical significance (P = .048).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Decreased cysteine and proline synthesis in parenterally fed, premature infants. 747 52

Procollagen I N-proteinase (EC 3.4.24.14), the enzyme that specifically processes type I and type II procollagens to collagen, was isolated from extracts of fetal calf skin. After two chromatographic steps on concanavalin A-Sepharose and heparin-Sepharose, the semi-purified preparation was used to produce monoclonal antibodies. One reacting antibody was found to recognize not the enzyme itself but type XIV collagen on which the enzyme was bound. This binding, highly sensitive to ionic conditions (plH, salt concentrations) but not affected by non-ionic detergents, was used for affinity chromatography that strongly improved the purification procedure. The enzyme is extensively characterized: 1) it has a molecular mass of 107 kDa as determined by polyacrylamide gel electrophoresis in presence of SDS and of about 130 kDa when estimated by gel filtration on a Sephacryl-S300; 2) in standard assay (pH 7.5, 0.2 M NaCl, 35 degrees C), the activation energy for reaction with amino procollagen type I was 17,000 calories per mole. In the same conditions, Km and Vmax values were, respectively, 435 and 39 nM per hour but varied strongly with pH and salt concentration; 3) the enzyme cleaved the NH2-terminal propeptide of type I procollagen at the specific site, the Pro-Gln bond in the alpha 1 type I procollagen chain; 4) the enzyme contained a high proportion of Gly, Asx, and Glx residues but no Hyp or Hyl; 5) partial amino acid sequences obtained from internal peptides of the enzyme displayed no significant homology with known sequences. The association of procollagen I N-proteinase with a FACIT (fibril-associated collagens with interrupted triple helices) collagen as found here might be of physiological significance.
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PMID:Characterization and partial amino acid sequencing of a 107-kDa procollagen I N-proteinase purified by affinity chromatography on immobilized type XIV collagen. 762 83

The binding of the fusion-inhibiting peptide Z-D-Phe-L-Phe-Gly to unilamellar lipid vesicles of dioleoylphosphatidylcholine (DOPC) was investigated by isothermal titration calorimetry (ITC). The peptide Z-D-Phe-L-Phe-Gly is known to inhibit fusion of myxo- and paramyxoviruses with cells as well as cell-cell and vesicle-vesicle fusion in model systems. Calorimetric titrations conducted over a range of temperatures permitted characterization of the thermodynamics of the interaction of Z-D-Phe-L-Phe-Gly with model DOPC lipid membranes. Simultaneous global analysis of 15 ITC binding curves acquired at four different temperatures allowed determination of the equilibrium site association constant (K), stoichiometry of binding (n), binding enthalpy change (delta H), and heat capacity change of binding (delta Cp) in a single set of experiments. The binding affinity and enthalpy change per mole of DOPC bound at 25 degrees C was log K = 2.463 +/- 0.075 and delta H = -1.07 +/- 0.12 kcal/mol DOPC while the binding heat capacity change per mole of DOPC bound was delta Cp = -20.3 +/- 2.8 cal/(K.mol DOPC) with a temperature dependence (from 10-45 degrees C) of d(delta Cp)/dT = 0.37 +/- 0.18 cal/(K2.mol DOPC). A temperature-independent binding stoichiometry was determined to be n = 5.56 +/- 0.33 DOPC molecules per Z-D-Phe-L-Phe-Gly. A comparison of these results with previous peptide-lipid binding studies is discussed as is their relevance to a current model of the interaction of fusion-inhibiting peptides with phospholipid membranes.
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PMID:Thermodynamics of interaction of the fusion-inhibiting peptide Z-D-Phe-L-Phe-Gly with dioleoylphosphatidylcholine vesicles: direct calorimetric determination. 762 21

Peptidylglycine alpha-amidating enzyme catalyzes the two-step conversion of C-terminal glycine-extended peptides to C-terminal alpha-amidated peptides and glyoxylate in a reaction that requires O2, ascorbate and 2 mol of copper per mole of enzyme [Kulathila et al. (1994) Arch. Biochem. Biophys. 311, 191-195]. Peptides with a C-terminal alpha-hydroxyglycine residue are intermediates in the amidation reaction. Benzylhydrazine inactivates the enzymatic conversion of dansyl-Tyr-Val-Gly to dansyl-Tyr-Val-NH2 in a time- and concentration-dependent manner. In contrast, the enzymatic conversion of dansyl-Tyr-Val-alpha-hydroxyglycine to dansyl-Tyr-Val-NH2 is unaffected by benzylhydrazine. The plot of 1/(inactivation rate) vs 1/[benzylhydrazine] is parabolic, indicating that the inactivation results from the interaction of 2 mol of benzylhydrazine per mole of enzyme. EPR spectra obtained from benzylhydrazine inactivation reactions carried out in the presence of a radical trap, alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone, show the formation of a carbon-centered benzyl radical. The benzyl radical most likely results from redox chemistry between benzylhydrazine and the enzyme-bound Cu(II) ions because EPR studies show that enzyme-bound Cu(II) is reduced to Cu(I) in the presence of benzylhydrazine. The kinetic constants for benzylhydrazine as a reductant in the amidation reaction were determined at benzylhydrazine concentrations too low to cause significant enzyme inactivation. Mimosine exhibits mixed inhibition vs benzylhydrazine; however, previous results have shown that benzylhydrazine is competitive vs ascorbate [Miller et al. (1992) Arch. Biochem. Biophys. 298, 380-388]. This change in kinetic mechanism coupled with the nonlinear inactivation kinetics have lead to a proposal that the two enzyme-bound Cu(II) atoms are nonequivalent with respect to their reduction by benzylhydrazine.
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PMID:The inactivation of bifunctional peptidylglycine alpha-amidating enzyme by benzylhydrazine: evidence that the two enzyme-bound copper atoms are nonequivalent. 787 9


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