Four- and five-step kinetic models of lactate dehydrogenase

1976 ◽  
Vol 54 (10) ◽  
pp. 915-918 ◽  
Author(s):  
Uwe Borgmann ◽  
Keith J. Laidler ◽  
Thomas W. Moon
Keyword(s):  
Lactate Dehydrogenase ◽  
Forward Direction ◽  
Reverse Direction ◽  
Similar Data ◽  
State Data ◽  
Incomplete Model ◽  
Step Model ◽  
The Relationship ◽  
Kinetics Of ◽  
Different Sources

A five-step model for the reaction catalyzed by beef heart lactate dehydrogenase (EC 1.1.1.27) reconciles differences observed in the four-step model if pre-steady-state data in the forward direction are compared with similar data in the reverse direction. The relationship between the four- and five-step models indicates what problems can develop when an incomplete model is proposed. Nevertheless, there are advantages to using the less complicated four-step model when comparing the molecular kinetics of enzymes catalyzing the same reaction but obtained from different sources.

scholarly journals Malate dehydrogenase of the cytosol. A kinetic investigation of the reaction mechanism and a comparison with lactate dehydrogenase

1978 ◽  
Vol 175 (3) ◽  
pp. 987-998 ◽  
Author(s):  
A Lodola ◽  
J D Shore ◽  
D M Parker ◽  
J Holbrook
Keyword(s):  
Steady State ◽  
Lactate Dehydrogenase ◽  
Malate Dehydrogenase ◽  
Forward Direction ◽  
Divergent Evolution ◽  
Reverse Direction ◽  
Enzyme Form ◽  
Active Substrate ◽  
Rate Limiting ◽  
Transient Measurements

1. The mechanisms of the reduction of oxaloacetate and of 3-fluoro-oxaloacetate by NADH catalysed by cytoplasmic pig heart malate dehydrogenase (MDH) were investigated. 2. One mol of dimeric enzyme produces 1.7+/-0.4 mol of enzyme-bound NADH when mixed with saturating NAD+ and L-malate at a rate much higher than the subsequent turnover at pH 7.5. 3. Transient measurements of protein and nucleotide fluorescence show that the steady-state complex in the forward direction is MDH-NADH and in the reverse direction MDH-NADH-oxaloacetate. 4. The rate of dissociation of MDH-NADH was measured and is the same as Vmax. in the forward direction at pH 7.5. Both NADH-binding sites are kinetically equivalent. The rate of dissociation varies with pH, as does the equilibrium binding constant for NADH. 5. 3-Fluoro-oxaloacetate is composed of three forms (F1, F2 and S) of which F1 and F2 are immediately substrates for the enzyme. The third form, S, is not a substrate, but when the F forms are used up form S slowly and non-enzymically equilibrates to yield the active substrate forms. S is 2,2-dihydroxy-3-fluorosuccinate. 6. The steady-state compound during the reduction of form F1 is an enzyme form that does not contain NADH, probably MDH-NAD+-fluoromalate. The steady-state compound for form F2 is an enzyme form containing NADH, probably MDH-NADH-fluoro-oxaloacetate. 7. The rate-limiting reaction in the reduction of form F2 shows a deuterium isotope rate ratio of 4 when NADH is replaced by its deuterium analogue, and the rate-limiting reaction is concluded to be hydride transfer. 8. A novel titration was used to show that dimeric cytoplasmic malate dehydrogenase contains two sites that can rapidly reduce the F1 form of 3-fluoro-oxaloacetate. The enzyme shows ‘all-of-the-sites’ behaviour. 9. Partial mechanisms are proposed to explain the enzyme-catalysed transformations of the natural and the fluoro substrates. These mechanisms are similar to the mechanism of pig heart lactate dehydrogenase and this, and the structural results of others, can be explained if the two enzymes are a product of divergent evolution.

NMR kinetic study of ligand exchange on a (µ-oxo)bis(µ-acetato)diruthenium(III) complex. A special kinetic case of introduction of a more labile ligand

1997 ◽  
Vol 75 (6) ◽  
pp. 890-898 ◽  
Author(s):  
Joana Mara Santos ◽  
Cecília Cipriano ◽  
Roberto B. Faria ◽  
J. Daniel Figueroa-Villar
Keyword(s):  
Ligand Exchange ◽  
Chemical Shifts ◽  
Variable Temperature ◽  
Forward Direction ◽  
Reverse Direction ◽  
H Nmr ◽  
Diruthenium Complex ◽  
Solvent Substitution ◽  
Kinetics Of ◽  
Oxo Bridge

We have prepared the new [Ru2(μ-O)(μ-O2CCH3)2(4-pic)6](PF6)2 complex and followed the kinetics of exchange of the 4-picoline ligands, trans to the oxo bridge, with dimethyl sulfoxide (DMSO-d6) by 1H NMR at 30, 40, 50, and 60 °C. The 1H NMR spectra of this complex in DMSO gradually change in the acetyl methyl region as solvent substitution of the 4-picoline trans to the oxo bridge takes place. This substitution is in accordance with the lability of the ligands trans to the RuIII-O-RuIII bridge in this kind of complex. The kinetic data fit in a series of double reversible reactions, pseudo first order in the forward direction and second order in the reverse direction, with ΔH≠ = 115, 105, 116, and 106 kJ mol−1 and ΔS≠ = 35.7, 17.2, 38.8, and 16.9 JK−1 mol−1 associated with k1, k−1, k2, and k−2 rate constants, respectively.[Formula: see text]A, B and C stand for the nonexchanged, monoexchanged, and diexchanged complexes, respectively. The large ΔH≠ and positive ΔS≠ values agree with the dissociative nature of the mechanism in both forward and reverse reactions. The differences in 1H and I3C NMR chemical shifts of the three complexes are explained in terms of the effect of the ligand exchange on the N—Ru bond lengths and the geometry of the dimetal core. It is evident from our data that the exchange on one metallic site modifies the reactivity at the other site in this kind of dinuclear complex. Keywords: diruthenium complex, variable temperature NMR, ligand exchange kinetics.

Determinants Considered by Consumers for Brand Selection - with Reference to Laptops in Albania

2014 ◽  
Vol 4 (2) ◽  
Author(s):  
Margret Plloçi ◽  
Macit Koc
Keyword(s):  
Primary Data ◽  
Battery Life ◽  
Decision Making Process ◽  
Light Weight ◽  
Sources Of Information ◽  
Technical Features ◽  
The Relationship ◽  
The City ◽  
Different Sources ◽  
Core Features

Abstract Purpose of the article There is relatively a big number of brands in the market of laptops nowadays in Albania. It appears that the number of brands offered in this market could easily be compared to the number of brands in Europe and even broader. The purpose of this study is to help Albanian vendors understand the criteria that consumers take into consideration when they make the decision to purchase a laptop. Methodology/methods The research is based on the collection and the analyses of the primary data collected through interviews to people like managers or employees who work in the sector of trading laptops or in businesses like education where laptops are broadly used recently; then a survey is done through a questionnaire delivered to customers who already own and use a laptop and customers who are potential buyers of laptops. Scientific aim The aim of the research is to identify if there are any relationships between the demographics of the consumers and the criteria of buying a laptop; on the other hand, to find out how is the relationship between the demographics and the features of different brands. Findings The study found out that Albanian consumers have good knowledge of laptops and their brands, and they use different sources of information for making their decisions in buying a laptop; it is found that there are relationships between some demographics like age or gender and the appraisal for some attributes of the laptops like price, design and high graphics card; it is also found that some technical features and other attributes of using laptops are some of the determinants that influence the laptops’ purchases. Conclusions It is realized that one of the most important demographics of the consumers is their age. Some core features like RAM, ROM, battery life, processor quality, light weight or attributes that are connected to the purposes of using the laptop computers like practicality and mobility in using them, work and studying processes, quick access to the internet are determinant factors which influence the decision making process of purchasing a laptop. I would recommend that future researches be focused also on the relationship between the customers’ income and their preferred brand or ranking brands according to the customers’ preferences. Such studies should also extend outside the city of Tirana.

Relation Between Metacognitive Ability with Science Process Skills on Grade 8th Students in MTs Negeri 3 Parigi

2020 ◽  
Vol 3 (1) ◽  
pp. 8-13
Author(s):  
Moch. Munir ◽  
Amiruddin Kade ◽  
Muslimin Muslimin
Keyword(s):  
Research Result ◽  
Reverse Direction ◽  
Process Skills ◽  
Science Process Skills ◽  
A Value ◽  
Regression Test ◽  
Feasibility Test ◽  
Relationship Of ◽  
The Relationship ◽  
Academic Year

This study aims to determine the relations between metacognitive to science process skills on grade VIII students MTs Negeri 3 Parigi. This research is descriptive, the approach used is a quantitative approach, manifested in the form of numbers analyzed by statistics and the results are described. The population is students of MTs Negeri 3 Parigi Academic Year 2017-2018 with a population of three classes, with a sample of 30 students. The instrument used is a metacognitive questionnaire consisting of 50 questions and an essay about science process skills 6 questions test. The result of the prerequisite test of the research result is all metacognitive indicators of normal and linear distributed and based on the regression feasibility test show that all data is feasible for regression test. The result of the regression test and test of determination to obtain a value which is not significant. Based on the results of the research analysis it can be concluded that the relationship of each metacognitive indicator to science process skills was not significant even there were metacognitive indicators that reverse direction significantly. The magnitude of the relationship of each metacognitive indicator with science process skills maximum 15.3%.  

Inactivation kinetics of Bacillus cereus vegetative cells and spores from different sources by antimicrobial photodynamic treatment (aPDT)

LWT ◽  
2021 ◽  
Vol 142 ◽  
pp. 111037
Author(s):  
Leonardo do Prado-Silva ◽  
Verônica O. Alvarenga ◽  
Gilberto Ú.L. Braga ◽  
Anderson S. Sant’Ana
Keyword(s):  
Bacillus Cereus ◽  
Inactivation Kinetics ◽  
Photodynamic Treatment ◽  
Vegetative Cells ◽  
Kinetics Of ◽  
Different Sources

scholarly journals Aromatic Profile Variation of Essential Oil from Dried Makwhaen Fruit and Related Species

Plants ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 803
Author(s):  
Trid Sriwichai ◽  
Jiratchaya Wisetkomolmat ◽  
Tonapha Pusadee ◽  
Korawan Sringarm ◽  
Kiattisak Duangmal ◽  
...  
Keyword(s):  
Cluster Analysis ◽  
Essential Oil ◽  
Related Species ◽  
Phenotypic Characteristic ◽  
Genetic Sequencing ◽  
Dried Fruits ◽  
Profile Variation ◽  
Chemical Profiles ◽  
The Relationship ◽  
Different Sources

The aim of this research is to evaluate the relationship between genotype, phenotype, and chemical profiles of essential oil obtained from available Zanthoxylum spp. Three specimens of makhwaen (MK) distributed in Northern Thailand were genetically and morphologically compared with other Zanthoxylum spices, known locally as huajiao (HJ) and makwoung (MKO), respectively. HJ was taxonomically confirmed as Z. armatum while MKO and MK were identified as Z. rhetsa and Z. myriacanthum. Genetic sequencing distributed these species into three groups accordingly to their confirmed species. Essential oil of the dried fruits from these samples was extracted and analyzed for their chemical and physical properties. Cluster analysis of their volatile compositions separated MKO and MK apart from HJ with L-limonene, terpinen-4-ol, β-phellandrene, and β-philandrene. By using odor attributes, the essential oil of MKO and MK were closely related possessing fruity, woody, and citrus aromas, while the HJ was distinctive. Overall, the phenotypic characteristic can be used to elucidate the species among makhwaen fruits of different sources. The volatile profiling was nonetheless dependent on the genotypes but makwoung and makhwaen showed similar profiles.

Oxidation of Olefins Representing Some Structural Units of GR-S

1952 ◽  
Vol 25 (1) ◽  
pp. 21-32 ◽  
Author(s):  
W. C. Warner ◽  
J. Reid Shelton
Keyword(s):  
Phenyl Group ◽  
Kinetic Mechanism ◽  
Oxidation Reactions ◽  
Chain Reaction ◽  
Instantaneous Rate ◽  
Initial Oxygen ◽  
Oxidation Of Olefins ◽  
A Minor ◽  
The Relationship ◽  
Kinetics Of

Abstract Three olefins were oxidized in the liquid phase with molecular oxygen to determine the kinetics of the oxidation reactions and the relationship to oxidation of rubber. The instantaneous rate of oxidation was found to be related to the analytically determined olefin and peroxide concentrations by the equation : Rate=k (unreacted olefin)(peroxide), where rate equals moles of oxygen per mole of original olefin per hour and the parentheses represent molarities. Presence of a phenyl group was found to affect k, but only in a minor way, indicating that the same fundamental kinetic mechanism applies in both aromatic and aliphatic olefins. The data are consistent with the general kinetic mechanism of Bolland involving oxygen attack at the alpha-methylenic group. However, it appears probable that initial oxygen attack can also occur at the double bond, resulting in the formation of a peroxide biradical, which may then react with other olefin molecules, initiating the usual chain reaction mechanism.

CORRELATION BETWEEN ELECTRIC CHARGING OF THE SAMPLE SURFACE AND KINETICS OF OPTICALLY STIMULATED EXOELECTRON EMISSION (OSEE) FROM CRYOSOLIDIFIED NaCl SOLUTION

1990 ◽  
Vol 04 (03) ◽  
pp. 201-209
Author(s):  
A. GIEROSZYŃSKI
Keyword(s):  
Electric Fields ◽  
Surface Potential ◽  
Surface Region ◽  
Sample Surface ◽  
Exoelectron Emission ◽  
Nacl Solution ◽  
Emitter Surface ◽  
Emitter Layer ◽  
The Relationship ◽  
Kinetics Of

It was found that OSEE kinetics from electron bombarded cryosolidified NaCl solution, depend on electric charging of the sample surface. It was shown that from the relationship between the maximum surface potential and the parameters of OSEE kinetic, intensities of electric fields in the emitter layer could be estimated. It is supposed that nonhomogeneous electric fields existing in the emitter surface region, influence the emission levels responsible for the course of OSEE kinetics.

TETANY AND PARATHYROID HYPERPLASIA IN THE NEWBORN INFANT: INFLUENCE OF DIETARY PHOSPHATE LOAD

PEDIATRICS ◽  
1952 ◽  
Vol 9 (5) ◽  
pp. 534-543
Author(s):  
LYTT I. GARDNER
Keyword(s):  
Differential Diagnosis ◽  
Cause Of Death ◽  
Newborn Infant ◽  
Newborn Infants ◽  
Parathyroid Hyperplasia ◽  
Similar Data ◽  
Older Children ◽  
Inorganic P ◽  
Dietary Phosphate ◽  
The Relationship

Three cases of newborn tetany are described, pointing out the relationship between dietary phosphate load and the manifestations of this disease. An additional three newborn infants are described who showed other symptomatology than tetany in association with dietary phosphate load. [See Table 1 in Source Pdf]. Data concerning diet, cause of death and degree of parathyroid hyperplasia are tabulated in eight newborns who were found to have parathyroid hyperplasia at autopsy. Similar data are tabulated on eight newborns and five older children who were found to have normal parathyroid glands at autopsy. Several other factors possibly involved in newborn tetany and newborn parathyroid hyperplasia are discussed. The importance of measuring serum inorganic P in the differential diagnosis of neonatal distress is pointed out.

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