Enzymes factors affecting rate

Lipases have also been used as initiators for the polymerization of lactones such as /3-bu tyro lac tone, <5-valerolactone, e-caprolactone, and macrolides.341,352-357 In this case, the key step is the reaction of lactone with die serine residue at the catalytically active site to form an acyl-enzyme hydroxy-terminated activated intermediate. This intermediate then reacts with the terminal hydroxyl group of a n-mer chain to produce an (n + i)-mer.325,355,358,359 Enzymatic lactone polymerization follows a conventional Michaelis-Menten enzymatic kinetics353 and presents a controlled character, without termination and chain transfer,355 although more or less controlled factors, such as water content of the enzyme, may affect polymerization rate and the nature of endgroups.360... 

MULTIPLE FACTORS AFFECT THE RATES OF ENZYME-CATALYZED REACTIONS... 

Rate of protein transfer to or from a reverse micellar phase and factors affecting the rate are important for the practical applications of RME for the extraction and purification of proteins/enzymes and for scale-up. The mechanism of protein exchange between two immiscible phases (Fig. 2) can be divided into three steps [36] the diffusion of protein from bulk aqueous solution to the interface, the formation of a protein-containing micelle at the interface, and the diffusion of a protein-containing micelle in to the organic phase. The reverse steps are applicable for back transfer with the coalescence of protein-filled RM with the interface to release the protein. The overall mass transfer rate during an extraction processes will depend on which of these steps is rate limiting. 

Now we can see the types of biochemical factors that determine the rate constant, fcbio for Michaelis-Menten cases the ability of the enzyme to catalyze the transformation as reflected by the quotient, kE/KiMM, and the presence of enzyme in the microorganism population involved, as quantified by [Enz]tot/[B], In the following section, we develop some detailed kinetic expressions for one case of enzyme-mediated transformations. Examination of these results will help us to see how structural features of xenobiotic compounds may affect rates. Finally, we will improve our ability to understand the relative rates for structurally related chemicals that are transformed by the same mechanism and are limited at the same biodegradation step. 

Factors affecting the rate of synthesis include the level of induction or repression of the gene encoding the enzyme (see Topics G3 and G4 and also the rate of degradation of the mRNA produced from that gene. Many key enzymes at control points in metabolic pathways have particularly short-lived mRNAs and the rate of enzyme synthesis is thus readily controlled by factors that affect the rate of gene transcription. 

Kinetics of Immobilized Enzymes. Another major factor in the performance of immobilized enzymes is the effect of the matrix on mass transport of substrates and products. Hindered access to the active site of an immobilized enzyme can affect the kinetic parameters in several ways. The effective concentration of substrates and products is also affected by the chemistry of the matrix especially with regard to the respective partition coefficients between the bulk solution and the matrix. In order to understand the effects of immobilization upon the rate of an enzyme-catalyzed reaction one must first consider the relationship between the velocity of an enzyme-catalyzed reaction and the... 

The rate of photosynthesis does not depend on the amount of a single component (e.g., the activity of a particular enzyme). There is a wide range of possible regulatory factors, proven to exist in vitro, but the importance of which in vivo has still to be determined. In particular, there is a multitude of factors affecting the activity of the enzymes involved, with pH, ions, coenzymes, and metabolite effectors modulating the activity of every enzyme studied thus far. Compartmentation is the other key factor. The role of metabolite transport in the cell, particularly between chloroplast and cytosol, but also to and from mitochondria, vacuole, and other organelles, is now considered to be fundamental to the regulation of photosynthesis. In this chapter, we look at the factors considered to be of major importance... 

Both the coenzyme-deficient apoenzymes and the holoenzymes may be present in serum. Therefore, addition of P-5 -P under conditions that allow recombination with the enzymes usually produces an increase in aminotransferase activity. In accordance with the principle that all factors affecting the rate of reaction must be optimized and controlled, IFCC recommends addition of P-5 -P in aminotransferase methods to ensure that all the enzymatic activity is measured. 

The activity of an enzyme is affected by environmental factors such as pH and temperature. Every enzyme has optimum conditions at which its reaction rate is fastest. In this ChemLab, you will study the decomposition of hydrogen peroxide as catalyzed by the catalase in carrot cells, and you will determine the optimum temperatures under which this enzyme works. 

A number of factors affect the rate and extent of protein degradation by proteolytic enzymes. These include the specificity of the enzyme, the extent of denaturation of the protein used as substrate as well as substrate and enzyme concentrations, pH, temperature and ionic strength of the reaction medium, presence of inhibitory substances, etc. It is beyond the scope of this review to discuss all these factors in detail. However, we do want to call attention to some of the more important factors and to refer the reader to articles such as those of Blow (15), Keil (16), and Killheffer and Bender (17). 

This chapter first explains enzyme nomenclature, describes enzymatic, supercritical reactor configurations, and gives a compilation of published experimental results. The- most important topics concerning enzymatic reactions in SCFs are then covered. These are factors affecting enzyme stability, the role of water in enzymatic catalysis, and the effect of pressure on reaction rates. Studies on mass transfer effects are also reviewed as are factors that have an effect on reaction selectivities. Finally, a rough cost calculation for a hypothetical industrial process is given. 

These two factors, binding, and Intrinsic electronic effects can be expected, therefore, to combine and to affect rates of turnover. Unfortunately, however. It Is not a simple task to dissect these two effects with any precision. Even though the Intrinsic electronic effects are known for a model reaction, the acid-catalysed hydrolysis of the same compounds, these cannot be applied directly to the enzymatic reaction since the absolute magnitude of such electronic effects depends upon the precise transition state structure. It Is very unlikely that these transition state structures for the enzyme-catalyzed and acid-catalyzed reactions will be Identical. 

Enzyme kinetics refers to the quantitative analysis of all factors that determine the catalytic potential of an enzyme. As presented in section 1.3, enzyme activity represents the maximum catalytic potential of an enzyme that is reflected by the initial rate of the catalyzed reaction. Several factors affect the expression of such potential, being the most important the concentrations of active enzyme, substrates and inhibitors, temperature and pH. In the case of insolubilized enzymes or multiphase systems, other variables that reflect mass transfer constraints must be considered. 

Conventionally, reaction rates in enzyme kinetics refer always to initial reaction rates where the maximum catalytic potential of the enzyme is expressed and many factors affecting it (i.e. substrate depletion, accumulation of inhibitory products, enzyme inactivation, reverse reaction) are irrelevant (see section 1.3). The quantification of such effects on that maximum catalytic potential is the subject of sections 3.2, 3.3 and 3.4. 

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