Biochemistry enzyme effects

Heterotropic allostery Especially in biochemistry, this effect occurs when a substance which is not an enzyme s substrate interacts to regulate the enzyme s activity. 

The field of organic chemistry has seen the most extensive use of polymeric materials as aids in effecting chemical transformation and product isolations. Polymers have been used in other, related areas of chemistry. Applications have been made in analytical chemistry (pH indicators and electrode modifiers), pharmaceutical and agricultural chemistry (controlled-release drugs, pesticides, herbicides, and fertilizers), and biochemistry (enzyme immobilization and affinity chromatography). Applications of polymers to solid-phase enzymo- and radioim-mune assays (Landon, 1977 Chard, 1978) will not be discussed since they are mainly analytical in scope. 

The most numerous cases of homogeneous catalysis are by certain ions or metal coordination compounds in aqueous solution and in biochemistry, where enzymes function catalyticaUy. Many ionic effects are known. The hydronium ion and the hydroxyl ion OH" cat-... 

Beanie, S. L., and Wolfenden, R., 1997. Mandelate racemase in pieces Effective concentrations of enzyme fnnctional groups in the transition state. Biochemistry 36 1646-1656. 

Hageman, R.H. Flesher, D. (1960). The effect of anaerobic environment on the activity of alcohol dehydrogenase and other enzymes of corn seedlings. Archives of Biochemistry and Biophysics, 87, 203-9. 

Enzymes are highly active catalysts in many biological processes. A very important feature in the catalytic action of enzymes is their high selectivity. Any enzyme that is active toward a particular reaction involving a particular substrate is entirely inactive toward other reactions and toward other substrates. (Note that in biochemistry, a substrate is the substance undergoing reaction under the catalytic effect of the enzyme.)... 

H. Bolton, L. F. Elliott, R, I, Papendick, and D, F. Bezdicek, Soil microbial biomass and selected soil enzyme activities effect of fertilisation and cropping practices. Soil Biology and Biochemistry 17 291 (1985),... 

In carrying out an enzyme assay it may be convenient to introduce an auxiliary enzyme to the system to effect the removal of a product produced by the first enzymatic reaction. McClure [Biochemistry, 8 (2782), 1969] has described the kinetics of certain of these coupled enzyme assays. The simplest coupled enzyme assay system may be represented as... 

This chapter describes a number of examples of kinetic isotope effects on chemical reactions of different types. These examples will be used to illustrate many aspects of the measurement, interpretation, and theoretical calculation of KIE s. Many of the examples are chosen from the field of organic chemistry. Chapter 11 deals with biochemistry, more specifically with enzyme chemistry. 

Historical Vignette 11.3] W. Wallace Cleland (1930-present) received his A.B. from Oberlin College in 1950 and his M.S. and Ph.D. from the University of Wisconsin-Madison in 1953 and 1955, respectively. After a postdoctoral fellowship spent at the University of Chicago he returned to Madison to join the faculty where he remains and is still actively involved in research. Cleland has devoted a great deal of time to developing and using isotope effect techniques to study enzyme mechanisms, see for example J. Biol. Chem. 278, 51975 (2003). (Photo credit Biochemistry Department, University of Wisconsin, Madison)... 

For the time being, our basic understanding of pressure effects is far from complete. However, some new developments concerning theory and application have occurred over the years. A short theoretical treatment of pressure effects was presented almost 30 years ago (Laidler, 1951). In this article we will present an extensive treatment of the present theoretical basis for pressure effects, incorporating contemporary knowledge of enzyme kinetics, physical biochemistry, and high-pressure theory. The theoretical level in this field is still not very sophisticated, but it is important enough so that theoretical considerations should be applied when future experiments are planned. 

Cook, P.F., Blanchard, J.S. and Cleland, W.W. (1980). Primary and secondary deuterium isotope effects on equilibrium constants for enzyme-catalyzed reactions. Biochemistry 19, 4853-4858... 

Klinman, J.P. (1976). Isotope effects and structure-reactivity correlations in the yeast alcohol dehydrogenase reaction. A study of the enzyme-catalyzed oxidation of aromatic alcohols. Biochemistry 15, 2018-2026... 

Karsten, W.E., Hwang, C.C. and Cook, P.F. (1999). Alpha-secondary tritium kinetic isotope effects indicate hydrogen tunneling and coupled motion occur in the oxidation of L-malate by NAD-malic enzyme. Biochemistry 38, 4398-4402... 

Karsten, W.E., Gavva, S.R., Park, S.H. and Cook, P.E. (1995). Metal ion activator effects on intrinsic isotope effects for hydride transfer from decarboxylation in the reaction catalyzed by the NAD-malic enzyme from Ascaris suum. Biochemistry 34, 3253-3260... 

Because the respiratory tract is an initial target of any air pollutant challenge, it usually receives primary attention in tests to determine irritant effects of exposure. Other aspects of interest include hematology, blood enzyme biochemistry, eye irritation, and p chomotor performance. Constriction of the large airways, maldistribution of ventilation due to narrowing in some small airways, constriction of peripheral lung units, and mechanical or gas diffusion impairment due to edema are possible effects of insult by pollutants. A variety of pulmonary tests is required to examine the possibilities. 

Figure 20.31 The principle of interconversion cycles in regulation of protein activity or changes in protein concentration as exemplified by translation/proteolysis or protein kinase/protein phosphatase. They result in very marked relative changes in regulator concentration or enzyme activity. The significance of the relative changes (or sensitivity in regulation) is discussed in Chapter 3. The principle of regulation by covalent modihcation is also described in Chapter 3. The modifications in cyclin concentration are achieved via translation and proteolysis, which, in effect, is an interconversion cycle. For the enzyme, they are achieved via phosphorylation and dephosphorylation reactions. In both cases, the relative change in concentration/activity by the covalent modification is enormous. This ensures, for example, that a sufficient increase in cyclin can occur so that an inactive cell cycle kinase can be converted to an active cell cycle kinase, or that a cell cycle kinase can be completely inactivated. Appreciation of the common principles in biochemistry helps in the understanding of what otherwise can appear to be complex phenomena.

The more we learn about the biology and biochemistry of DNA methylation, the more fascinating and challenging the field becomes. The last decade has witnessed a significant progress in our knowledge we learned that there are many enzymes involved in methylation/demethylation of DNA we appreciated the discovery of proteins that bind specifically to methylated DNA sequences to recruit numerous other proteins with a variety of functions we realized that the effect of DNA... 

Haiech, J. Klee, C.B. Demaille, J.G. Haiech, J. Effects of cations on affinity of calmodulin for calcium ordered binding of calcium ions allows the specific activation of calmodulin-stimulated enzymes. Theoretical approach to study of multiple ligand binding to a macromolecule. Biochemistry 1981, 20, 3890-3897. 

High pressure has proven to be a useful tool in biochemistry for the study of a number of cell-mediated processes, the most important being the effect on gene expression. The pressure effect on the stability of enzymes and biopolymers is a topic of general interest that may generate a number of possible applications in the area of food science. Biochemistry and biophysics continue to attract many new research groups, especially in the field of protein chemistry. Pressure may be a tool to obtain unique textures and provide biochemical products with new properties. 

K,y can then be obtained from a plot of v against [D] if the receptor concentration is constant. This is, of course, the same as the direct plot of enzyme activity shown in every biochemistry textbook. As with all hyperbolic relationships, there are several drawbacks to this technique many data points are needed at the beginning of the curve, at low [D] values, where accuracy is limited. Also, determination of the maximum effect is almost impossible, since we are dealing with an asymptotic curve. 

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