Enzymatic reactions characterization

The Michaelis constant is equal to substrate concentration at which the rate of reaction is equal to one-half the maximum rate. The parameters and characterize the enzymatic reactions that are described by Michaelis-Menten kinetics. is dependent on total... 

Saturation kinetics are also called zero-order kinetics or Michaelis-Menten kinetics. The Michaelis-Menten equation is mainly used to characterize the interactions of enzymes and substrates, but it is also widely applied to characterize the elimination of chemical compounds from the body. The substrate concentration that produces half-maximal velocity of an enzymatic reaction, termed value or Michaelis constant, can be determined experimentally by graphing r/, as a function of substrate concentration, [S]. 

As discussed in the early sections it seems that there are very few effective ways to stabilize the transition state and electrostatic energy appears to be the most effective one. In fact, it is quite likely that any enzymatic reaction which is characterized by a significant rate acceleration (a large AAgf +p) will involve a complimentarity between the electrostatic potential of the enzyme-active site and the change in charges during the reaction (Ref. 10). This point may be examined by the reader in any system he likes to study. 

Martmez-Parra, J. and Munoz, R., An approach to the characterization of betanine oxidation catalyzed by horseradish peroxidase, J. Agric. Food Chem., 45, 2984, 1997. Martmez-Parra, J. and Munoz, R., Characterization of betacyanin oxidation catalyzed by a peroxidase from Beta vulgaris L. roots, J. Agric. Food Chem., 49, 4064, 2001. Ashie, l.N.A. Simpson, B.K., and Smith, J.P., Mechanisms for controlling enzymatic reactions in foods, Crit. Rev. Food Sci. Nutr., 36, 1, 1996. 

The biological membranes that surround cells and form the boundaries of intracellular organelles contain polyunsaturated fiitty acids, which are susceptible to oxidation. This reaction is used under controlled conditions by enzymes, such as the lipoxygenases or cyclooxygenases, within cells to produce oxygenated lipids, which can act as mediators of inflammation (Smith and Marnett, 1991 Yamamoto, 1992). Such compounds are characterized by their high potency and specificity in their interaction with cells (Salmon, 1986). While these enzymatic reactions... 

The CES family of proteins is characterized by the ability to hydrolyze a wide variety of aromatic and aliphatic substrates containing ester, thioester, and amide bonds (Heymann 1980, 1982). Cauxin is a member of the CES family, and is secreted from the proximal straight tubular cells into the urine in a species-, sex-, and age-dependent manner. Therefore, we postulated that cauxin was involved in an enzymatic reaction in cat urine and the products made by the reaction should vary with species, sex, and age. Based on this hypothesis, we searched for physiological substrates and products of cauxin in cat urine and identified 2-amino-7-hydroxy-5,5-dimethyl-4-thiaheptanoic acid, also known as felinine. 

Since the enzymatic reactions are generally rapid, it may be assumed that the steady-state approximation applies. Note, however, that although true is most systems, this is not always the case, as exemplified in Section 5.2.5. Each half-reaction is characterized by three rate constants, defined in Scheme 5.1. They may alternatively be characterized by the following... 

The path computation has been most successful when applied to a specific class of binary relations, namely the substrate-product relations of enzymatic reactions. They constitute a well-characterized set of binary relations, and the amount of available data is relatively large. There are about 3,500 main reactions between the main compounds that are represented in the KEGG pathway diagrams. An enzymatic reaction generally involves multiple substrates and multiple products, so that it must first be decomposed into all possible substrate-product binary relations. However, because the relations involving ubiquitous compounds such as water and ATP will make many undesired connections, it is better to limit to main compounds for practical purposes. 

The enzymatic reaction mechanism was determined by incubating a-carotene 6, a non-symmetric substrate of the enzyme, under a 02 atmosphere in H2 0 followed by isolation and characterization of derivatives of the cleavage product 2 (6). Accordingly, the enzyme cleaving the central double bond of 1 was found to be a non-heme iron monooxygenase (P-carotene 15,15 -monooxygenase) and not dioxygenase as termed earlier (Fig. 3). From the chemical point of view this enzymatic reaction is very unusual for various reasons (i) the reaction... 

Over the last 30 years an ever increasing amount of information on the biosynthesis of oxime intermediates in plant metabolism and on interactions of oximes with enzymes has accumulated. Enzymatic reactions that were characterized with respect to oximes as products, substrates or inhibitors are listed in Table 2. 

The mechanism of an enzymatic reaction is ultimately defined when all the intermediates, complexes, and conformational states of the enzyme are characterized and the rate constants for their interconversion are determined. The task of the kineticist in this elucidation is to detect the number and sequence of these intermediates and processes, define their approximate nature (that is, whether covalent intermediates are formed or conformational changes occur), measure the rate constants, and, from studying pH dependence, search for the participation of acidic and basic groups. The chemist seeks to identify the chemical nature of the intermediates, by what chemical paths they form and decay, and the types of catalysis that are involved. These results can then be combined with those from x-ray diffraction and NMR studies and calculations by theoretical chemists to give a complete description of the mechanism. 

Kinetic analysis was used to characterize enzyme-catalyzed reactions even before enzymes had been isolated in pure form. As a rule, kinetic measurements are made on purified enzymes in vitro. But the properties so determined must be referred back to the situation in vivo to ensure they are physiologically relevant. This is important because the rate of an enzymatic reaction can depend strongly on the concentrations of the substrates and products, and also on temperature, pH, and the concentrations of other molecules that activate or inhibit the enzyme. Kinetic analysis of such effects is indispensable to a comprehensive picture of an enzyme. 

Enzymes are biological catalysts. Kinetic analysis is one of the most broadly used tools for characterizing enzymatic reactions. 

Enzyme kinetics deals with the rate of enzyme reaction and how it is affected by various chemical and physical conditions. Kinetic studies of enzymatic reactions provide information about the basic mechanism of the enzyme reaction and other parameters that characterize the properties of the enzyme. The rate equations developed from the kinetic studies can be applied in calculating reaction time, yields, and optimum economic condition, which are important in the design of an effective bioreactor. 

NCE is a relatively new development in separation science, especially in proteomics and genomics. In the last two decades NCE has gained increasing importance, as can be seen from a good number of publications [17-20]. In addition to the above advantages, NCE is a suitable technique for samples that may be difficult to separate by NLC as the principles of separation are entirely different. Lower detection limits of NCE lead to the possibility of separating and characterizing small quantities of materials. Moreover, the enzymatic reactions for analytical purposes can be conducted within the capillary. 

Partial lipid extraction is considered as biologically important in several processes involving membranes, for example the fusion of membranes or enzymatic reactions with participation of phospholipids. To simulate this process, non-equilibrium or steered MD simulations can be used. This type of simulation was employed for the first time by Grubmuller et al. [96] to study the rupture of the binding in the strepta-vidin-biotin complex. Inspired by this pioneering work, similar studies have been undertaken to characterize the extraction of a phospholipid from the membrane. 

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