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1

Kinetic properties of AMP deaminase in acute experimental pancreatitis

100%
Kossowska E., Purzycka-Preis J., Wozniak M., Zydowo M., Sledzinski Z.
Acta Biochimica Polonica
|
1994
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tom 41
|
nr 2
2
Artykuł dostępny w postaci pełnego tekstu - kliknij by otworzyć plik
Content available

Kinetics properties of polyphenol oxidase in hawthorn (Crataegus spp.)

75%
Saeidian S.
International Letters of Natural Sciences
|
2014
|
tom 20
Polyphenol oxidase (PPO) from hawthorn was extracted and partially purified through (NH4)2SO4 precipitation, dialysis and ion exchange chromatography. The activity of polyphenol oxidase was investigated in Crataegus spp. Spectrophotometric method was used to assay the enzyme activity and the kinetic constants - maximum enzyme velocity (Vmax) and Michealis - Menten constant (Km). Of the substrates tested, catechol was the best substrate for PPO with a Km value of 2.2 mM. The optimum pH for PPO activity was found to be 7. The enzyme showed high activity over a broad pH range of 4 - 8. The optimal pH and temperature for enzyme activity were found to be 7 and 40-45 °C, respectively. km value for hawthorn PPO is calculated 22 mM for catechol and 6.7 mM for pyrogallol and 9.7 mM for L-dopa. As can be seen, affinity of PPOs for various substrates varies widely. The enzyme showed a broad activity over a broad pH and temperature range. The thermal inactivation studies showed that the enzyme is heat resistant. The enzyme showed the highest activity toward pyrogallol and no activity toward tyrosine. Of the inhibitors tested, the most potent inhibitors were kojic acid, cysteine and glycine , respectively.
3

Comparison of the kinetic properties of the pyruvate dehydrogenase complex from pig kidney cortex and medulla

75%
Pawelczyk T., Olson M. S.
Acta Biochimica Polonica
|
1993
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tom 40
|
nr 3
The activity of the pyruvate dehydrogenase complex (PDC) purified from pig kidney medulla was affected by K+, Na+, CI", HCO3"", HP042" and changes in ionic strength. Increased ionic strength influenced the activity of PDC from medulla by decreasing the Vmax and S0.5 for pyruvate and increasing the Hill coefficient. The magnitude of these changes was smaller than the corresponding changes for PDC purified from the cortex. In the presence of K+ (80 mM), Na+ (20 mM), Cl~ (20 mM), HCO3" (20 mM), HPO42" (10 mM) and at ionic strength of 0.15 M the S0.5 for pyruvate of PDC from medulla was 117 nM and the enzyme complex was saturated by 1.1 mM pyruvate. Under these conditions the S0.5 for pyruvate of PDC derived from cortex was 159 nM and the enzyme was saturated at 4.5 mM pyruvate.
4
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The impact of intake canal geometry on kinematics of load in combustion chamber

63%
Piatkowski P.
Teka Komisji Motoryzacji i Energetyki Rolnictwa
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2012
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tom 12
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nr 1
5

Isolation and some properties of malic enzyme from the abdomen muscle of Antarctic krill Euphausia superba

63%
Napierska D., Skorkowski E. F.
Bulletin of the Sea Fisheries Institute
|
2001
|
nr 1
6
Content available remote

Effect of quercetin on kinetic properties of renal Na,K-ATPase in normotensive and hypertensive rats

51%
Mezesova L., Bartekova M., Javorkova V., Vlkovicova J., Breier A., Vrbjar N.
Journal of Physiology and Pharmacology
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2010
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tom 61
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nr 5
The effect of quercetin, a plant-derived bioflavonoid with documented positive effect on the cardiovascular system, was examined after 4-week supplementation in the dose of 20 mg kg-1·day-1 to young male normotensive control (C) and to spontaneously hypertensive rats (SHR) over the period of their 5th-8th week of age. The study was focused on the influence of quercetin on properties of the renal Na,K-ATPase, a key system in maintaining the homeostasis of sodium in the organism. Spontaneous hypertension by itself enhanced the activity of Na,K-ATPase probably as a consequence of a higher number of active enzyme molecules, as suggested by the 15% increase of Vmax, along with improved affinity to ATP, as indicated by the 30% decrease in the value of Michaelis-Menten constant Km in untreated SHR vs. untreated normotensive rats. Quercetin induced a decrease of Na,K-ATPase activity in the presence of all ATP and Na+ concentrations investigated. Evaluation of kinetic parameters resulted in a constant Vmax value. The ATP-binding properties of the enzyme were not influenced by quercetin, as suggested by statistically insignificant changes in the value of Km both in controls and in SHR. On the other hand, the affinity to sodium decreased, as suggested by an increase in the KNa value by 22% and 31% in normotensive and hypertensive groups, respectively. This impairment in the affinity of the Na+-binding site of Na,K-ATPase molecules was probably responsible for the deteriorated enzyme function in the kidneys of quercetin treated animals.
7

Drying kinetics and textural properties of pears dehydrated by combined method with application of vacuum-microwaves

51%
Lech K., Siudek M., Michalska A., Figiel A.
Zeszyty Problemowe Postępów Nauk Rolniczych
|
2016
|
tom 586
Pear cubes were dehydrated by convective drying (CD) and by combined method consisting of convective pre-drying (CPD) and vacuum-microwave finish-drying (VMFD). During combined method the time of CPD lasted for 15, 30 and 120 min. The VMFD of pear cubes was performed at magnetrons power of 240, 480 and 720 W. The drying kinetics of pear cubes was described using a modified Page model. The entire drying time of combined drying was reduced by earlier application of VMFD with higher microwave power. Pear cubes dried by the combined method had a lower density and crispier texture as compared to the samples dried only by convective method. An increase in pre-drying time resulted in a decrease in the density and compressive strength, whereas increase in microwave power reduced the density of the dried products.
8

Przemiany fazowe składników odżywek w proszku dla niemowląt

51%
Ostrowska-Ligeza E., Szulc K., Lenart A.
Zeszyty Problemowe Postępów Nauk Rolniczych
|
2010
|
tom 553
Odżywki w proszku dla niemowląt są to układy wieloskładnikowe. Celem pracy była analiza przemian fazowych poszczególnych składników oraz ich wpływ na właściwości termokinetyczne odżywek w proszku. Proszki spożywcze były badane przy użyciu skaningowego kalorymetru różnicowego (DSC). Pełny termogram proszku otrzymywano w wyniku ogrzewania próbki od temperatury -60°C do temperatury 160 lub 300°C z szybkością 5K/min., w atmosferze azotu. Zaobserwowano różnice w przebiegu termogramów laktozy krystalicznej i amorficznej. Termogram laktozy krystalicznej charakteryzuje się dwoma pikami endotermicznymi, natomiast laktoza amorficzna charakteryzuje się pikiem egzo- i endotermicznym. Tłuszcz mleczny charakteryzuje się tylko pikami endotermicznymi. Białka mleka i skrobia mają termogramy o łagodnym przebiegu, również endotermicznym. Na podstawie przebiegu krzywych można zaobserwować odpowiednie piki przemian fazowych w termogramach mleka pełnego i odtłuszczonego. W termogramach odżywek dla niemowląt zaobserwowano charakterystyczne piki topnienia laktozy, jako jednego z głównych składników tych mieszanin. W zależności od zawartości tłuszczu można zaobserwować jego przemiany fazowe w odżywkach. Na podstawie termogramów składników można wykazać ich obecność na termogramach odżywek w proszku dla niemowląt.
9

Expression, purification and kinetic properties of human recombinant phospholipase C delta3

51%
Pawelczyk T., Matecki A.
Acta Biochimica Polonica
|
1997
|
tom 44
|
nr 2
To obtain sufficient quantities of pure phospholipase C delta 3 (PLC delta 3) necessary for structural and kinetic studies, cDNA of human fibroblast PLC delta 3 was cloned in the pPROEX-1 vector, expressed in E. coli cells as a (6 x His) fusion protein and purified to homogeneity. From 1 L of E. coli culture 8 mg of pure PLC delta 3 was obtained by a two step purification procedure, which includes phosphocellulose and Mono S cation exchange chromatography. The presence of His tag did not affect the catalytic and regulatory properties of PLC delta 3. The K(app) for PIP2 was 142 +/- 11 and 156 +/- 12 microM for His.PLC delta 3 and PLC delta 3, respectively. Recombinant PLC delta 3 showed an absolute requirement for Ca2+. Increasing the free Ca2+ concentration from 0.2 to 0.5 microM resulted in a sharp increase in enzyme activity. In comparison with human recombinant PLC delta 1 the delta 3 isoenzyme was more sensitive to low Ca2+ concentration. The Ca2+ concentration yielding maximal activation of PLC delta 1 and PLC delta 3 was 10 and 1 microM, respectively. The activity of PLC delta 3 was stimulated by polyamines and by basic proteins such as protamine, histone and mellitin. PLC delta 3 was activated most effectively by spermine and histone but the extent of this activation was lower than for PLC delta 1. The data presented indicate that the expression of PLC delta 3 in E. coli cells permits to obtain active enzyme. The catalytic and regulatory properties of PLC delta 3 are similar to those of PLC delta 1.
10

Cultivar variation in heat stability and kinetic properties of soluble invertase in wheat grains

51%
Asthir B., Kaur A., Basra A. S.
Acta Physiologiae Plantarum
|
1998
|
tom 20
|
nr 4
Soluble invertase from mid-milky stage grains of two wheat (Triticum aestivum L.) varieties, namely Kalyansona and PBW 343 was isolated and purified by employing ammonium sulphate precipitation, gel filtration on Sephadex G-150 and DEAE-cellulose column chromatography. Invertase from Kalyansona exhibited greater heat stability (50 °C) compared to PBW 343 (35 °C). By employing photo-oxidation and chemical modification methods, and by studying the effect of pH on Km and Vmax, the involvement of histidine, sulphydryl and α-carboxyl groups in the active site of the enzyme was indicated. The enzyme was completely inhibited by HgCl₂ and DTNB. ZnSO₄, MgSO₄, KCl, CaCl₂, EDTA and pyridoxine were strong inhibitors in PBW 343 but not in Kalyansona. The two varieties also showed differential response in respect to thermodynamic properties of the enzyme, i.e. energy of activation (Ea), enthalpy change (ΔH) and entropy change (ΔS). Overall the results suggest that genetic differences exist in soluble invertase properties of wheat grains and that the thermal adaptation of the enzyme is reflected in its altered kinetic behaviour.
11

Pyruvate kinase - a key enzyme of glycolysis in the tissues of selected snails of Poland

45%
Rybska E., Lesicki A.
Folia Malacologica
|
1998
|
tom 06
|
nr 1-4
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