Enzyme Structure and Function

James, M.N.G. An x-ray crystallographic approach to enzyme structure and function. Can. J. Biochem. 

All metals, regardless of whether they are essential or nonessential, can exhibit toxic effects at high concentrations.14-16 Excess concentrations of essential metals can lead to nonspecific binding, which can affect the enzyme structure and function. Because controlling metal concentrations is vital for maintaining homeostatic conditions within bacterial cells, evolution has bestowed upon organisms a number of ways to regulate concentrations of essential metals and to resist the toxicity of nonessential metals.17-20... 

The development of magnetic resonance techniques coupled with computer time averaging has made the study of enzyme structure and function by these techniques more fruitful. H NMR, 13C NMR and 19F NMR have been used successfully to determine the structure of B 12-compounds in solution. We are rapidly approaching the point where the structure and function of the B 12-coenzymes will be completely understood, and the need for the synthesis and study of simple Bi2-model compounds such as the cobaloximes (3) will be no longer necessary. However, even though studies on the chemistry of B 12-coenzymes is a necessary prerequisite to our understanding of their biochemical role, it is a wrong assumption to expect that the chemical properties of free coenzymes in aqueous solution should be duplicated in the enzymes. 

Sola-Penna, M., A. Ferreira-Pereira, A.P. Lemos, and J.R. Meyer-Femandes. 1997. Carbohydrate protection of enzyme structure and function against guanidinium chloride treatment depends on the nature of carbohydrate and enzyme. Eur J Biochem 248 24—29. 

Herein we provide a general overview of enzymatic catalysis in organic solvents, with a focus on the role of water and solvent on enzyme structure and function, and how an increased knowledge of this role has led to methods to activate enzymes for optimal use in organic media. 

Removing Water from Enzymes-the Effect of Lyophilization on Enzyme Structure and Function... 

Enzymes are basically specialty proteins (qv) and consist of amino acids, the exact sequence of which determines the enzyme structure and function. Although enzyme molecules are typically very large, most of the chemistry involving the enzyme takes place in a relatively small region known as the active site. In an enzyme-catalyzed reaction, binding occurs at the active site to one of the molecules involved. This molecule is called the substrate. Enzymes are... 

Fersht, A. (1985). Enzyme Structure and Function, pp. 109-111. Freeman, New York. Fischer, G. (1989). Nova Acta Leopold. 61, 35-53. 

General enz.ymology is discussed effectively in numerous standard treatises, and one of the must concise discussions appears in the classic work by Ferdinand, who includes reviews of enzyme structure and function, biuenergetics. and kinetics and appropriate illustrations with a total of 37 enzymes. selected from the six major classc.s. For additional basic Studies of enzymolugy. the reader should refer to this cla.ssic monograph and to a coniprehcn.sive review of this topic. ... 

Many enzymes use the flavin cofactor at the active site the fluorescent active site approach can be applied to study these enzymes at the single-molecule level. Other naturally fluorescent enzymes, like those that contain NAD cofactors, can in principle be studied, although the bluer fluorescence of NAD poses a technical challenge for singlemolecule fluorescence detection. As the approach uses the natural fluorescence of the enzyme, no labeling with fluorescent probes is needed, offering no or minimum perturbation on the enzyme structure and function. 

The present chapter focuses on the effects of environmental stress on enzyme structure and function and the various mechanisms that respond to these stresses to alter enzyme function (and metabolic pathways). Many examples will be drawn from animals that live at environmental extremes, for it is here that we find the principles of enzyme structure and function most clearly illustrated. Because this subject is complex and covers a wide variety of different fields, the present chapter will highlight key principles using selected enzymes as examples. The reader is referred to other sources for more exhaustive treatments of individual topics in comparative biochemistry and enzyme adaptation (Crowe and Clegg, 1978 Ho-chachka and Somero, 1984 Gilles, 1985 Bowler and Fuller, 1987 Storey, 1988 Storey and Storey, 1988). 

Low, P. S. Somero, G. N. (1975). Pressure effects on enzyme structure and function in vitro and under simulated in vivo conditions. Comp. Biochem. Physiol. 52B, 67-74. 

Enzyme Structure and Function in Water-Restricted Environments... 

Recent research has demonstrated that enzymes can function in various low-water environments (1-4), and that the properties of enzymes can be favorably modified by nonaqueous solvents (5-7). Increased substrate solubility, reversal of hydrolytic reactions, and improved thermostability are among the practical advantages afforded by nonaqueous solvents. However, the role of water in enzymatic reactions at low water concentrations is not generally understood, and there is some uncertainty regarding how much the conformation of a protein changes as solvent water is removed (8.9). Nonaqueous solvent systems therefore represent important media in which to examine enzyme structure and function at the molecular level. Such studies will prove valuable for the application of enzymes in low-... 

Now that the principles of enzymatic architecture and the corresponding analysis strategies have been highlighted and briefly discussed, an overview of the existing enzyme classes and their properties is needed. Given the more than 4000 different enzyme types, any attempt at only listing them would be far beyond the scope of this chapter. Fortunately, there are a number of specialized databases available, which aim to treat various aspects of enzyme structure and function comprehensively. All of these databases are accessible via the Internet, and a list of the relevant URL addresses is given in Table 5-1. 

Kathryn M. McCulloch received her Bachelor s degree in chemistry from Ball State University, Muncie, IN, in 2004. She is now at Cornell University pursuing her doctoral degree with Professor Steven Ealick and studying enzyme structure and function through X-ray crystallography. 

Whereas the field of enzymology has primarily concerned small-molecule metabolic pathways over the past 80 years, there is a growing interest in focusing on enzyme structure and function that relates to protein posttranslational modifications. It is now believed that posttranslational modifying pathways are hierarchically elevated in the context of governing cell... 

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