Enzymes conditions

The reaction is exactly analogous to the chemical aldol reaction (also shown), but it utilizes an enamine as the nucleophile, and it can thus be achieved under typical enzymic conditions, i.e. around neutrality and at room temperature. There is one subtle difference though, in that the enzyme produces an enamine from a primary amine. We have indicated that enamine formation is a property of secondary amines, whereas primary amines react with aldehydes and ketones to form imines (see Section 7.7.1). Thus, a further property of the enzyme is to help stabilize the enamine tautomer relative to the imine. 

On the other hand, alkaline phosphatase may have two equivalent active sites which are coupled so that, normally, only one can operate at a time. This seems an attractive alternative for an enzyme consisting of two identical subunits. In a preliminary paper, Lazdunski et al. (125) report the covalent incorporation of two phosphates into the zinc enzyme as well as the cobalt enzyme, at >H<4. At these low pH values, the free enzyme generally loses its metal ions and dissociates into monomeres (109). However, if these results are corroborated after the performance of proper controls, and if both phosphates are linked to specific amino acid residues in the enzyme, conditions may have been found for the uncoupling of active sites in alkaline phosphatase. 

The development of a commercially viable enzyme process for the production of ECB nucleus was achieved by improving the ECB and ECB deacylase fermentation processes and the bioconversion processes. Increased yields in the fermentation processes were achieved through linked programs for strain improvement and fermentation development. The bioconversion process was improved by the choice of substrate and enzyme conditions and subsequent optimization of operating conditions. An economic model was used to decide where development resources should be focused. 

A study was conducted to elucidate the mechanism of FeMo-cofactor catalytic activity in non-enzymic conditions and to compare its catalytic behavior with that of the nitrogenase (Bazhenova et al., 2000). The kinetics were investigated of C2H2 redaction by multielectron donors, Zn and Eu amalgams, catalyzed by isolated FeMo-cofactor and... 

The reverse of sulfation is desulfation, which can be effected under mild enzymic conditions [96]. Similarly, enzymic depolymerization, closely guarded by trade secrets, is routinely used in the production of heparin-derived dmgs. 

Enzymic conditions by an NADH system could reform vitamin C. Although the biological activity, presumably its antioxidancy, is said to be preserved in the acetate this is almost lost in its ethers and thus the phenolic group is a vital functional group. 

Fig. 1 Shear stress as a function of shear rate for different times during the initial 4-h enzymatic hydrolysis and fermentation, a 10, b 15, and c 20% solids concentration, a-c Enzyme condition 30 FPU/g of glucan, pH 4.8 to 5.0, 50 °C, 120 rpm. d SFF condition 30 FPU/g of glucan, pH 4.8 to 5.0, 30 °C 120 rpm, Zymomonas mobilis, strain 39679 pZB4L...

Another type of technique that may be employed takes advantage of continuous culture in a chemostat to provide extremely high levels of a desired enzyme. Conditions that have been used include growth on limiting concentration-levels of the substrate of the desired enzyme, and... 

In this book we will be concerned with reactions of dioxygen mediated by transition metal complexes under non-enzymic conditions, where complexation is responsible for lifting the restriction imposed by spin conservation (case II). 

Figure 7. Thermal denaturatlon of LBI (lower right) and Its complexes with trypsin (bovine, BT porcine, PT) or bovine a-chymotrypsin (XT). Arrows at top and bottom of Figure show positions of peaks for the free enzymes. Conditions pH 6.7 0.05 M KCl, 0.02 M CaCl2 heating rate, 10 C/m1n.

From our results, there is no evidence that methionine or tryptophan combine covalently with alkali- or enzymically-gene-rated quinones. Methionine however may be extensively oxidized by the quinones to its sulphoxide. Lysine, on the other hand, undoubtedly forms covalent linkages with quinones and two possible reaction pathways are shown in Fig. 4. The proposed schemes take into consideration our findings (Hurrell et al., 1982) that lysine-caffeoquinone complexes formed under alkaline and enzymic conditions are probably different, and that each bound lysine... 

Pabacatalytic Modification op Various Enzymes. Conditions and Effect on Enzymic Activity ... 

Compounds are transformed into each other by chemical reactions that can be run under a variety of conditions from gas-phase reactions in refineries that produce basic chemicals on a large scale, through parallel transformations of sets of compounds on well-plates in combinatorial chemistry, all the way to the transformation of a substrate by an enzyme in a biochemical pathway. This wide range of reaction conditions underlines the complicated task of imderstanding and predicting chemical reaction events. 

It should be noted that a number of different enzyme preparations can now be purchased directly from manufacturing chemists. It must be emphasised that the activity of an enzyme, whether purchased or prepared in the laboratory, may vary between rather wide limits. The activity is dependent on the source of the enzyme, the presence of poisons and also on the temperature. It appears, for example, that the quality of horseradish peroxidase depends upon the season of the year at which the root is obtained from the ground. It cannot be expected therefore that all the experiments described below will work always with the precision characteristic of an organic reaction proceeding under accurately known conditions. 

Enzymatic resolution (Section 7 13) Resolution of a mixture of enantiomers based on the selective reaction of one of them under conditions of enzyme catalysis... 

A plot of equation 13.18, shown in figure 13.10, is instructive for defining conditions under which the rate of an enzymatic reaction can be used for the quantitative analysis of enzymes and substrates. Eor high substrate concentrations, where [S] Kjq, equation 13.18 simplifies to... 

Selectivity The analysis of closely related compounds, as we have seen in earlier chapters, is often complicated by their tendency to interfere with one another. To overcome this problem, the analyte and interferent must first be separated. An advantage of chemical kinetic methods is that conditions can often be adjusted so that the analyte and interferent have different reaction rates. If the difference in rates is large enough, one species may react completely before the other species has a chance to react. For example, many enzymes selectively cat-... 

The enzyme fumarase catalyzes the stereospecific addition of water to fumarate to form L-malate. A standard solution of fumarase, with a concentration of 0.150 tM, gave a rate of reaction of 2.00 tM mim under conditions in which the concentration of the substrate was significantly greater than K. The rate of reaction for a sample, under identical conditions, was found to be 1.15 tM mimh What is the concentration of fumarase in the sample ... 

An enzyme digest is the term applied to a process whereby a peptide or protein is mixed with a selected enzyme under favorable conditions to allow reaction to occur. The enzyme splits the peptide or protein into smaller units that are easier to identify. 

Cortisol-Cortisone Conversion. Under normal conditions, this equilibrium slightly favors the oxidized compound. Similarly, the conversion of corticosterone to 11-deoxycorticosterone is also mediated by the liP-hydroxysteroid dehydrogenase enzyme system and requites NAD(P) /NAD(P)H. This conversion is especially important both in the protection of the human fetus from excessive glucocorticoid exposure, and in the protection of distal nephron mineral ocorticoid receptors from glucocorticoid exposure (14). The impairment of this conversion is thought to result in hypertension associated with renal insufficiency (15). 

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