Canadian Science Publishing
0008-4018
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Các bài báo tiêu biểu
Jack bean urease (EC 3.5.1.5). V. On the mechanism of action of urease on urea, formamide, acetamide, N-methylurea, and related compounds Acetamide and N-methylurea have been shown for the first time to be substrates for jack bean urease. In the enzymatic hydrolysis of urea, formamide, acetamide, and N-methylurea at pH 7.0 and 38 °C, kcat has the values 5870, 85, 0.55, and 0.075 s−1 , respectively. The urease-catalyzed hydrolysis of all these substrates involves the active-site nicke... ... hiện toàn bộ
Tập 58 Số 12 - Trang 1335-1344 - 1980
A Cytokinin Oxidase in Zea mays An enzyme activity that catalyzes conversion of N6 -(Δ2 -isopentenyl)adenosine (i6 Ado) to adenosine was detected in cultured tobacco tissue by Pačes et al. (1971) (Plant Physiol. 48, 775–778). Purification and characteristics of this enzyme in corn kernels have been studied. Only the naturally occurring cytokinins i6... hiện toàn bộ
Tập 52 Số 9 - Trang 789-799 - 1974
Structural determination of the polysaccharide antigens of Neisseria meningitidis serogroups Y, W-135, and BO The purified high molecular weight serogoup Y meningococcal polysaccharide contains equimolar proportions of D-glucose and N-acetylneuraminic acid and is partially O-acetylated. Carbon-13 nuclear magnetic resonance (NMR) studies, together with other chemical data, have indicated that the polysaccharide is linked only at C-6 of the D-glucose and C-4 of the sialic acid residues, all the lin... ... hiện toàn bộ
Tập 54 Số 1 - Trang 1-8 - 1976
Identification and Distribution of Tryptamine in the Rat A procedure for the quantitative measurement of tryptamine in mammalian tissues is described. The amine is isolated by ion-exchange chromatography, converted to its dansyl derivative, further purified by thin-layer chromatography, and quantitated by the mass-spectrometric integrated ion current technique using an isotopically labelled internal standard.The concentrations of tryptamine in ... ... hiện toàn bộ
Tập 52 Số 6 - Trang 447-451 - 1974
Jack bean urease (EC 3.5.1.5). IV. The molecular size and the mechanism of inhibition by hydroxamic acids. Spectrophotometric titration of enzymes with reversible inhibitors Kinetic, spectral, and other studies establish that hydroxamic acids bind reversibly to active-site nickel ion in jack bean urease. Equilibrium ultracentrifugation studies establish that the molecular weight of native urease is 590 000 ± 30 000 while that of the subunit formed in 6 M guanidinium chloride in the presence of β-mercaptoethanol is ~95 000. Essentially the same subunit molecul... ... hiện toàn bộ
Tập 58 Số 12 - Trang 1323-1334 - 1980
A MODIFIED YEMM AND COCKING NINHYDRIN REAGENT FOR PEPTIDASE ASSAYA modified Yemm and Cocking ninhydrin–cyanide reagent has been developed which gives quantitative color yields with free amino acids, but much lower yields with most peptides tested. Using this reagent, a more sensitive assay for peptidase activity has been developed, and its use in column fractionation of peptidase activity is described.The ϵ values for peptides, obtained with the modifie... ... hiện toàn bộ
Tập 42 Số 1 - Trang 95-103 - 1964
Purification and Properties of Rat Liver Nuclear Protein Kinases Two protein kinases, designated NI and NII, have been isolated from rat liver nuclei. These enzymes have a similar pH optimum and phosphorylate phosvitin and casein more readily than histone. Both enzymes require magnesium for activity. In the absence of Mg2+ , other divalent cations such as Ca2+ , Co2+ , and Mn2+... hiện toàn bộ
Tập 50 Số 12 - Trang 1249-1259 - 1972
Amino acid sequence alignment of bacterial and mammalian pancreatic serine proteases based on topological equivalences The three-dimensional structures of the bacterial serine proteases SGPA, SGPB, and α-lytic protease have been compared with those of the pancreatic enzymes α-chymotrypsin and elastase. This comparison shows that ~60% (55–64%) of the α-carbon atom positions of the bacterial serine proteases are topologically equivalent to the α-carbon atom positions of the pancreatic enzymes. The correspon... ... hiện toàn bộ
Tập 56 Số 6 - Trang 396-402 - 1978
Evidence for albumin – Cu(II) – amino acid ternary complex Commercially obtained pure human serum albumin (HSA) was shown to contain molecular aggregates and was significantly contaminated with Cu(II). A solution of commercial HSA was first passed through a Sephadex G-200 column to obtain pure monomeric HSA. The monomer of HSA was subsequently passed through Chelex-100 resin to free it from Cu(II). All Cu(II)-binding studies were conducted with m... ... hiện toàn bộ
Tập 46 Số 6 - Trang 601-607 - 1968
Decreased monoamine oxidase activity in liver of iron-deficient rats Chronic nutritional deficiency of iron in the rat results in a decrease of 18–31% in the monoamine oxidase activity of the liver. Prolonged feeding of a diet low in copper was without effect on the enzyme, although the concentration of ceruloplasmin in the plasma and of copper in the liver declined.Possible roles of iron in the action of monoamine oxidase are discussed. The inhibitory act... ... hiện toàn bộ
Tập 47 Số 11 - Trang 999-1002 - 1969