Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Resting cells of Corynebacterium nephridii reduce nitrate, nitrite, and nitric oxide to nitrous oxide under anaerobic conditions. Nitrous oxide production from nitrite was optimal from pH 7.0 to 7.4. The stoichiometry of nitrous oxide production from nitrite was 99% of the theoretical-two moles of nitrite was used for each mole of nitrous oxide detected. Hydroxylamine increases gas evolution from nitrite but inhibits the reduction of nitric oxide to nitrous oxide. Hydroxylamine is converted to nitrogenous gas(es) by resting cells only in the presence of nitrite. Under certain conditions nitric oxide, as well as nitrous oxide, was detected.
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PMID:Production of nitric oxide and nitrous oxide during denitrification by Corynebacterium nephridii. 543 50

Peroxidase from the obligate chemosynthetic bacterium Nitrosomonas europaea was purified 1,500-fold, and its properties were examined. The enzyme had a molecular weight of 53,000 and exhibited characteristic absorption maxima at 410, 524, and 558 mmu. The optimal pH and temperature were 7.5 and 44 C, respectively. The peroxidase reaction had an energy of activation of 5,850 cal/mole and required a primary substrate (H(2)O(2)) concentration of 7 x 10(-6)m to proceed at half maximal velocity (K(m)). Reduced cytochrome, c,p-phenylenediamine and pyrogallol acted as hydrogen donors to the purified peroxidase-H(2)O(2) complex. Conditions most suitable for the chemical oxidation of ammonium by H(2)O(2) were determined. The reaction was rapid and produced nitrite but no nitrate. Hydroxylamine was not detected as an intermediate, but it could substitute for ammonium in the system. Neither the rate nor the extent of these reactions was influenced by purified peroxidase, and no evidence was obtained to support a conclusion that the enzyme performs a vital role in the transformation of ammonium to nitrite by N. europaea.
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PMID:Purification and properties of peroxidase from Nitrosomonas europaea. 566 76

When 125I-labeled thrombin was incubated with washed human platelets or with the supernatant solution of activated platelets, it formed a NaDodSO4-stable complex of apparent mass greater than 450 000 daltons. Formation of the complex was temperature dependent; with 20 nM thrombin incubated with the supernatant solution of ionophore-activated platelets, the initial rate of formation of the stable complex was 1 nM thrombin/min at 37 degrees C, 50 times the rate at 22 degrees C. Thrombin with all free amino groups methylated was still reactive. Active-site-blocked thrombin formed the complex only slowly. The complex that formed with active thrombin was not dissociated by hydroxylamine in urea. Reduction with 2-mercaptoethanol dissociated the complex, and its formation was blocked by the sulfhydryl-blocking agents iodoacetamide and 4,4'-dithiodipyridine. The complex was thus unlike those of thrombin and alpha 2-macroglobulin or antithrombin III, but it had characteristics of a disulfide-linked complex. Of the secreted proteins, albumin and glycoprotein G adhered to an activated thiol-Sepharose column, indicating that they contained free thiol groups. Purified glycoprotein G and thrombin formed a complex similar to the complex formed when thrombin was incubated with the supernatant solution of activated platelets. The purified glycoprotein bound 2.6 mol of radioactive N-ethylmaleimide/mol of protein, indicating three sulfhydryl groups per mole. After reacting with purified glycoprotein G, thrombin developed a new sulfhydryl group. It is concluded that glycoprotein G (thrombin-sensitive protein, thrombospondin) and thrombin form a dissociable complex that leads to a covalent complex by thiol-disulfide exchange of a thiol group on glycoprotein G and a disulfide on thrombin.
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PMID:Formation of a stable complex of thrombin and the secreted platelet protein glycoprotein G (thrombin-sensitive protein, thrombospondin) by thiol-disulfide exchange. 643 45

Diethyl pyrocarbonate inhibited diaphorase activity of ferredoxin-NADP+ oxidoreductase with a second-order rate constant of 2 mM-1 X min-1 at pH 7.0 and 20 degrees C, showing a concomitant increase in absorbance at 242 nm due to formation of carbethoxyhistidyl derivatives. Activity could be restored by hydroxylamine, and the pH curve of inactivation indicated the involvement of a residue having a pKa of 6.8. Derivatization of tyrosyl residues was also evident, although with no effect on the diaphorase activity. Both NADP+ and NADPH protected the enzyme against inactivation, suggesting that the modification occurred at or near the nucleotide binding domain. The reductase lost all of its diaphorase activity after about two histidine residues had been blocked by the reagent. In differential-labeling experiments with NADP+ as protective agent, it was shown that diaphorase inactivation resulted from blocking of only one histidyl residue per mole of enzyme. Modified reductase did not bind pyridine nucleotides. Modification of the flavoprotein in the presence of NADP+, i.e., with full preservation of diaphorase activity, resulted in a significant impairment of cytochrome c reductase activity, with a second-order rate constant for inactivation of about 0.5 mM-1 X min-1. Reversal by hydroxylamine and spectroscopic data indicated that this second residue was also a histidine. Ferredoxin afforded only slight protection against this inhibition. Conversely, carbethoxylation of the enzyme did not affect complex formation with the ferrosulfoprotein. Redox titration of the modified reductase with NADPH and with reduced ferredoxin suggested that the second histidine might be located in the electron pathway between FAD and ferredoxin.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Essential histidyl residues of ferredoxin-NADP+ oxidoreductase revealed by diethyl pyrocarbonate inactivation. 668 70

The proteinaceous coat associated with the cytoplasmic side of milk lipid globule membranes (MLGM) was prepared from bovine and caprine milk by removal of membrane material with non-ionic detergent. These coat preparations, which were enriched in two major proteins, a glycoprotein of polypeptide M, 67 000 (butyrophilin) and a non-glycosylated protein of polypeptide Mr 155 000 (xanthine oxidase), contained small amounts of fatty acids which could not be removed by exhaustive extractions with organic solvents. Both butyrophilin and xanthine oxidase of bovine MLGM were excised and eluted from SDS-polyacrylamide gels and were shown to contain 1 to 2 moles of bound fatty acids per mole of protein. Palmitic, stearic and oleic acids were the predominant protein-bound fatty acids, but no specificity for binding of individual fatty acids was observed. The fatty acids were not rendered soluble in organic solvents when the protein preparations were incubated with phospholipases A or C or with trypsin. Treatment with 0.25 M NaOH at 100 degrees C for 1 h or with 1 M hydroxylamine at 4 degrees C for 16 h, however, released virtually all of the fatty acids associated with these proteins. Similar results were obtained with two major proteins, bands 3 and 4.1, or rat erythrocyte plasma membrane. By contrast, skeletal muscle actin and serum albumin had no bound fatty acids that could be released by alkali treatment. These results show that fatty acids are bound to a number of membrane-associated proteins, both glycosylated and unglycosylated, via linkages that resist purification of the proteins on SDS-polyacrylamide gel electrophoresis and are suggestive of covalent attachment of fatty acids to these proteins. The possible involvement of this acylation in processes characterized by local changes of membrane shape and plasticity is discussed.
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PMID:Tight attachment of fatty acids to proteins associated with milk lipid globule membrane. 706 4

Affinity-purified polyclonal antibodies prepared against a synthetic peptide corresponding to sequence 18-29 from the N-terminus of rabbit alpha-skeletal actin reacted with G- and F-actin. Epitope mapping experiments with thrombin and hydroxylamine cleaved actin, and immunochemical assays verified the specificity of antibodies for the 18-29 sequence on actin. The binding of up to 0.5 mol of IgG per mole of actin did not affect the rigor binding of myosin subfragment 1 (S-1) to actin. Similarly, the binding of IgG to actin was not changed by a complete saturation of actin by S-1. In contrast to this, the weak acto-S-1 interactions in the presence of ATP were strongly inhibited by the 18-29 antibodies. At 25 degrees C, the acto-S-1 ATPase activity was inhibited by IgG stronger than the binding of S-1.ATP gamma S to actin. Thus, at this temperature, a catalytic inhibition of the acto-S-1 system appears to account at least in part for the antibody effect. Acto-S-1 ATPase activities at 25 degrees C were inhibited also by F(ab)(18-29). At 5 degrees C, the acto-S-1 ATPase activity and the binding of S-1.ATP to actin were inhibited approximately to the same extent by IgG(18-29). These results are discussed in terms of S-1 binding sites on actin and the possible role of sequence 18-29 in actomyosin interactions.
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PMID:Role of sequence 18-29 on actin in actomyosin interactions. 768 58

A mixed microbial culture capable of metabolizing the explosive RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) was obtained from soil enrichments under aerobic and nitrogen-limiting conditions. A bacterium, Stenotrophomonas maltophilia PB1, isolated from the culture used RDX as a sole source of nitrogen for growth. Three moles of nitrogen was used per mole of RDX, yielding a metabolite identified by mass spectroscopy and 1H nuclear magnetic resonance analysis as methylene-N-(hydroxymethyl)-hydroxylamine-N'-(hydroxymethyl)nitroamin e. The bacterium also used s-triazine as a sole source of nitrogen but not the structurally similar compounds octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine, cyanuric acid, and melamine. An inducible RDX-degrading activity was present in crude cell extracts.
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PMID:Degradation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) by Stenotrophomonas maltophilia PB1. 774 53

Human urinary DNase I was inactivated by monoiodoacetate and monobromoacetate. The inactivation was greater at pH 7.2 than at 6.0 and proceeded in the presence of Ca2+. Amino acid analysis of monobromoacetate-inactivated human urinary DNase I indicated that one histidine residue per mole of the enzyme reacted with monobromoacetate. Diethylpyrocarbonate also inactivated the enzyme, which was protected by DNA in the presence of Mg2+. However, oligonucleotides did not prevent the inactivation even in the presence of Mg2+. Hydroxylamine almost completely restored the activity of the inactivated enzyme by DEP. One histidine residue per mole of the enzyme was calculated to be modified, as shown by the difference spectra of DEP-inactivated enzyme. This histidine residue seems to react with the substrate. These results provide evidence that human urinary DNase I possesses one essential histidine residue at the active site.
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PMID:Evidence for an essential histidine residue on active site of human urinary DNase I: carboxymethylation and carbethoxylation. 805 72

The effect of a transmembrane peptide on the domain structure of a two-component, two-phase lipid bilayer composed of dimyristoyl phosphatidylcholine (DMPC) and distearoyl phosphatidylcholine (DSPC) was examined by spin label electron spin resonance (ESR) spectroscopy. The peptide, pOmpA, is the hydrophobic, 25-residue signal sequence of the outer membrane protein A from Escherichia coli. Nitroxide derivatives of the phospholipid DSPC, 16-DSPCSL, and of the pOmpA signal peptide, pOmpA-IASL, were used as probes. The first-derivative lineshapes of the ESR spectra were analyzed using a normalized intensity ratio, R, that gives information on the average sizes of the disconnected fluid domains and their point of connectivity (Sankaram, M.B., D. Marsh, and T.E. Thompson. 1992. Biophys. J. 63:340-349). In the absence of the peptide, the number of fluid lipid domains does not vary with the fraction of lipid that is in the fluid phase, and phase conversion is accomplished solely by changes in the domain size. The phase boundaries of the lipid mixture remain largely unchanged by the presence of the peptide at mole fractions up to 0.02, but both the size and number of the fluid domains is changed, and the point at which they become connected is shifted to lower fractions of the fluid phase. In addition, the number of domains in the presence of the peptide no longer remains constant but increases from a domain density at low fractions of the fluid phase that is much lower than that in the absence of peptide to one that is comparable to the natural state in the absence of peptide at the point of domain connectivity. A simple model is presented for the process of domain fission, where the latter is determined by a balance between the effects of peptide concentration in the fluid domains, the line tension at the domain boundaries, and the distributional entropy of the domains.
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PMID:Reorganization of lipid domain structure in membranes by a transmembrane peptide: an ESR spin label study on the effect of the Escherichia coli outer membrane protein A signal peptide on the fluid lipid domain connectivity in binary mixtures of dimyristoyl phosphatidylcholine and distearoyl phosphatidylcholine. 807 30

Mutagenesis of the H5 region of the Shaker K+ channel has provided strong evidence that these amino acids form a major portion of the ionic pore. We have previously observed that a single-site mutation (T441S) in this region increased the apparent relative permeability of the channel to NH4+. We now report that this increased relative permeability to NH4+ is sensitive to small changes in external K+ in a pattern consistent with an anomalous mole fraction effect. The effect is not apparent in the wild-type channel. These findings, in combination with other studies showing effects of this particular mutation on the binding of tetraethylammonium and hydroxylamine, support the hypothesis that T441S alters the affinity of a putative ion binding site for NH4+ and ammonium derivatives. The mutation T441S alters ionic selectivity and reveals the multi-ion nature of the mutant Shaker K+ channel.
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PMID:Anomalous mole fraction effect induced by mutation of the H5 pore region in the Shaker K+ channel. 891 86


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