Canadian Science Publishing
0008-4018
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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
Tập 58 Số 12 - Trang 1335-1344 - 1980
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 nickel ion(s). Enzymatic hydrolysis of the following
com...
A Cytokinin Oxidase in Zea mays
Tập 52 Số 9 - Trang 789-799 - 1974
An enzyme activity that catalyzes conversion of N6-(Δ2-isopentenyl)adenosine
(i6Ado) 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 i6Ado and ribosylzeatin serve as substrates; the nucleoside or free
base works equally...
Structural determination of the polysaccharide antigens of Neisseria meningitidis serogroups Y, W-135, and BO
Tập 54 Số 1 - Trang 1-8 - 1976
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
linkages bei...
Identification and Distribution of Tryptamine in the Rat
Tập 52 Số 6 - Trang 447-451 - 1974
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 some
tiss...
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
Tập 58 Số 12 - Trang 1323-1334 - 1980
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
molecular weight...
A MODIFIED YEMM AND COCKING NINHYDRIN REAGENT FOR PEPTIDASE ASSAY
Tập 42 Số 1 - Trang 95-103 - 1964
A 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
modified reagen...
Purification and Properties of Rat Liver Nuclear Protein Kinases
Tập 50 Số 12 - Trang 1249-1259 - 1972
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+ can
substitute partially for Mg2+ when the reaction is catalyzed by NI. With NII,
only ...
Amino acid sequence alignment of bacterial and mammalian pancreatic serine proteases based on topological equivalences
Tập 56 Số 6 - Trang 396-402 - 1978
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
corresponding valu...
Evidence for albumin – Cu(II) – amino acid ternary complex
Tập 46 Số 6 - Trang 601-607 - 1968
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 monomeric ...
STUDIES ON THE LIPID METABOLISM OF THE CHICK EMBRYO
Tập 42 Số 12 - Trang 1729-1741 - 1964
A study was made of the amounts and fatty acid compositions of the cholesterol
esters, phospholipids, and triglycerides present in the yolk of the fertile
unincubated egg and in the yolk, liver, and extrahepatic tissues of the chick
embryo at various stages of development. Esterification of cholesterol, mainly
with oleic acid, occurred in the yolk during incubation. There appeared to be a
preferen...