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Enzymatic Reaction Kinetics
Published in Debabrata Das, Debayan Das, Biochemical Engineering, 2019
Although many enzymes have similar names, they are acquired from different organisms. In addition, these enzymes have different catalytic activity, e.g., glucose isomerase. It has been found that glucose isomerase obtained from B. coagulans requires Co2+, whereas glucose isomerase from a mutant of B. coagulans does not require Co2+ at a pH greater than 8. A specific enzymatic activity indicates the purity of an enzyme and is expressed as micromoles of substrate converted per minute per milligram of protein. Enzymatic activity is also expressed as turnover number. It is defined as the number of substrate molecules reacted per catalyst site per unit time. A comparative study on enzymes and solid-catalyzed reactions reveals that some enzymatic reactions are faster than non-biological catalytic reactions, e.g., papain (proteolytic enzyme).
Recent Advances in Enzyme Immobilization Using Nanomaterials and its Applications for the Production of Biofuels
Published in Madan L. Verma, Nanobiotechnology for Sustainable Bioenergy and Biofuel Production, 2020
Sujit Sadashiv Jagtap, Ashwini Ashok Bedekar
The turnover number is defined as the number of times each enzyme site converts substrate to product per unit time (Eisenthal et al. 2007). The different enzymes show different turnover numbers after immobilization. The quantity of each enzyme can be controlled in the immobilized multi-enzymatic system. The substrate specificity and product inhibition of the enzyme are important parameters for the immobilized multi-enzymatic system. The enzyme should be substrate selective and unaffected by the products of other immobilized enzymes. The use of cofactor-regenerating enzymes reduces the cost of the immobilized multi-enzymatic system (Wichmann and Vasic-Racki 2005).
Enzymatic Reaction Kinetics and Immobilization of Enzymes
Published in Debabrata Das, Soumya Pandit, Industrial Biotechnology, 2021
Enzymatic activity is expressed via the international unit (I.U.). 1 I.U. is defined as the amount of the enzyme that catalyses the conversion of one micromole of substrate per min under specified conditions. Specific enzymatic activity is expressed as micromole of substrate converted per min/mg of protein. Enzymatic activity may also be expressed as a turnover number where protein molecules have more than one active site. This is possible in the case of larger protein molecules. The turnover number is defined as the number of substrate molecules reacted per catalyst site per unit time.
Synthesis and characterization of a new 4-styrylpyridine based square planar copper(II) complex: exploration of phenoxazinone synthase-mimicking activity and DFT study
Published in Journal of Coordination Chemistry, 2019
Akhtaruz Zaman, Samim Khan, Basudeb Dutta, Sobhy M. Yakout, Shebl S. Ibrahim, Mohammad Hedayetullah Mir
All these enzyme kinetic plots have been used to evaluate several kinetic parameters, including turnover number (kcat) and specificity constant (kcat/KM) for phenoxazinone synthase-mimicking activity of the complex. In enzyme kinetics, turnover number (also termed as kcat) is defined as the maximum number of catalytic conversions of substrate molecules per unit of time that a single catalytic site will execute for a specific enzyme concentration. The specificity constant (also termed as kcat/KM ratio) is a measure of how efficiently a catalyst converts substrates into products. This ratio is a useful index for measuring the substrate specificity of catalyst. The higher the specificity constant, the more the enzyme prefers that substrate. Figures 5 and S2 represent the Michaelis–Menten plot, Lineweaver–Burk plot, Hanes–Woolf plot and Eadie–Hofstee plot for catalytic oxidation of OAPH in methanol and in 20% methanol, respectively. Tables 2 and S4 contain kinetic parameters for phenoxazinone synthase-mimicking activity in methanol and in 20% methanol, respectively.
A sustainable preparative-scale chemo-enzymatic synthesis of 6-hydroxy-5,7-dimethoxy-2-naphthoic acid (DMNA) from sinapic acid
Published in Green Chemistry Letters and Reviews, 2022
Amandine L. Flourat, Nour Zeaiter, Erwan Vallée, V. P. Thinh Nguyen, Sami Fadlallah, Florent Allais
The Kcat or enzymatic turnover number is calculated based on the initial speed of the reaction (mol.L−1.min−1) divided by the concentration of the enzyme (mol.L−1). Thus, it indicates the efficiency of the catalytic system. The maximal productivity gives the quantity of substrate formed per minute of reaction if the reaction was stopped at the optimum time or after 5 h for an uncomplete reaction.