Properties of enzymes

As with normal chemical reactions, there are many reasons for studying the kinetics of enzyme-catalysed reactions to be able to predict how the rate of reaction will be affected by changes in reaction conditions to aid in the determination of the 

An understanding of the influence of environmental conditions on the kinetics of enzyme reactions is essential for the design of processes based upon the use of these materials as catalysts. Their growth kinetics are also governed by similar kinetic equations (c.f. Monod growth equations, Section S.9). 

In five respects, the catalytic activity of enzymes differs from that of other catalysts. 

The stereochemical specificity of enzymes depends on the existence of at least three different points of interaction, each of which must have a binding or catalytic function. A catalytic site on the molecule is known as an active site or active centre of the enzyme. Such sites constitute only a small proportion of the total volume of the enzyme and are located on or near the surface. The active site is usually a very complex physico-chemical space, creating micro-environments in which the binding and catalytic areas can be found. The forces operating at the active site can involve charge, hydrophobicity, hydrogen-bonding and redox processes. The determinants of specificity are thus very complex but are founded on the primary, secondary and tertiary structures of proteins (see Appendix 5.1). 

Transferases—Transference of an atom or group between two molecules, 

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The catalytic properties of enzymes are reflected in K, and kcat values... 

Dixon, M., et al., 1979. Enzymes, 3rd ed. New York Academic Press. A classic work on enzyme kinetics and die properties of enzymes. 

Section I deals with the structures and functions of proteins and enTymes, the workhorses of the body. Because almost all of the reactions in cells are catalyzed by enzymes, it is vital to understand the properties of enzymes before considering other topics. 

Schenk S, A Hoelz, B Krauss, K Decker (1998) Gene structures and properties of enzymes of the plasmid-encoded nicotine catabolism of Arthrobacter nicotinovorans. J Mol Biol 284 1323-1339. 

Table 2 Properties of enzymes foimd in cannabinoid biosynthesis... 

Table 6. Comparison of properties of enzymes involved in biodesulfurization...

Most of the pesticide biosensors are designed based on the inhibitory property of enzymes. AChE and butyrylcholinesterase (BChE) are widely used in the development of pesticide biosensors [17, 18], Inhibition leads to a decrease in activity, which... 

Manipulation of one enzymatic step in a system can have wide reaching consequences because of the interplay between metabolite levels and a wide range of regulatory circuits. These circuits can operate at the level of transcription, translation, post-translational modification, or through allosteric and competitive influences on the kinetic properties of enzymes. 

Scheme 1 is a gross over-simplification for almost any enzyme-catalyzed reaction of a specific substrate, based as it is on a one-step reaction with a single, rate-determining transition state but it is appropriate for many, if not most reactions catalyzed by simple enzyme mimics. Most important for present purposes, it emphasises the most important properties of enzyme reactions which the design of mimics, or artificial enzymes, must address, namely ... 

Scientists have studied the amazing properties of enzymes and catalysts for more than 200 years. 

Other examples of efficient enzymatic resolutions by reaction at a remote position from stereocentres have been reported, such as the lipase-catalysed resolution of a synthetic intermediate of escitalopram." This property of enzymes has also been effectively used to resolve sterically hindered compounds by the introduction of a tether so that the enzyme-catalysed reaction can be performed at an artificially created, but less hindered, remote location. An example is the resolution of tertiary alcohols by the introduction of a glyoxylate ester. 

Table 1.4 Kinetic Properties of Enzymes Used in Cyclic Systems...

The reasons for the effect of pH on the catalytic properties of enzymes are numerous and will not be discussed here. For most enzymes, however, there is a pH at which they are optimally effective changing the pH to lower (more acidic) levels or to higher (more basic) levels will decrease the overall rate at which the associated chemical reaction occurs. In the region of the optimum pH, the reaction rate vs. pH response surface can usually be approximated reasonably well by a second-order, parabolic relationship. 

The amygdaline electrode [47] that does not find extensive practical apph-cation is suitable as a model for investigation of the properties of enzyme electrodes in general [36], because of its specific response. The electrode is based on the reaction... 

All these uses depend upon one or both of the two paramount properties of enzymes catalytic power and specificity. 

Punyasiri PA, Abeysinghe IS, Kumar V, Treutter D, Duy D, Gosch C, Martens S, Eorkmann G, Fischer TC (2004) Flavonoid biosynthesis in the tea plant Camellia sinensis properties of enzymes of the prominent epicatechin and catechin pathways. Arch Biochem Biophys 431(l) 22-30... 

The catalytic properties of enzymes, and consequently their activity (see p. 90), are influenced by numerous factors, which all have to be optimized and controlled if activity measurements are to be carried out in a useful and reproducible fashion. These factors include physical quantities (temperature, pressure), the chemical properties of the solution (pH value, ionic strength), and the concentrations of the relevant substrates, cofactors, and inhibitors. 

Kim, S., Benoiton, L. and Paik, WK. (1964) Epsdon-Alkyllysinase -Purification 4- Properties of Enzyme. The Journal of Biological Chemistry,... 

Effect of immobilization on the dynamic properties of enzymes. Examples of three different experimentally imposed conditions include (a) enzyme and substrate are present in an aqueous solution (b) enzyme and substrate are immobilized on or within a solid support and (c) immobilized enzyme acts on a substrate present within an aqueous solution. The rate laws and curves that are presented below each diagram indicate the expected rate behavior. (From K. J. Laidler P. S. Bunting (1982) Meth. Enzymol. 64, 229.)... 

Another of the most important properties of enzymes as catalysts is that they are not changed during the reactions they catalyze, which allows a single enzyme to catalyze a reaction many times. 

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