Work and Enzymes

The second characteristic implicit in the macromolecules is that they are all extremely unlikely substances. Those materials which life produces in such abundance still defeat the synthetic techniques of the chemist. In the living cell, such molecules cannot arise purely by random chemical reactions they must be synthesized according to precisely planned pathways which can achieve a specificity far beyond that of the chemist. There must be mechanisms within the cell which can distinguish between even such close relatives as the ( + ) and (—) isomers of amino acids, or between sugars such as glucose and galactose. 

So before it can even begin to act on its external environment, the cell, or the living animal, has to provide the mechanisms whereby, first, it can protect itself against dissolution and des- 

This law of the conservation of energy makes it easy to understand the concept of work in a physical system, but it is not immediately obvious that work and energy are factors in chemical reactions too. Consider, however, the combination of carbon and oxygen to give carbon dioxide. We write the equation 

As with the body, so with the cell and, in describing the many chemical syntheses and activities of the cell, we must at the same time ask also from where the energy for the performance of this work has come. 

The principal source of energy for the cell is, of course, glucose. 

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The genome, through its constituent DNAs, provides all of the codes needed for building a wide range of peptides, proteins, and enzymes, which in turn utilize raw materials (food) to form an animate body and keep it going. These multiple reactions work together as a unit within a water-filled cell. 

Chirazymes. These are commercially available enzymes e.g. lipases, esterases, that can be used for the preparation of a variety of optically active carboxylic acids, alcohols and amines. They can cause regio and stereospecific hydrolysis and do not require cofactors. Some can be used also for esterification or transesterification in neat organic solvents. The proteases, amidases and oxidases are obtained from bacteria or fungi, whereas esterases are from pig liver and thermophilic bacteria. For preparative work the enzymes are covalently bound to a carrier and do not therefore contaminate the reaction products. Chirazymes are available form Roche Molecular Biochemicals and are used without further purification. 

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

B. Studies of Equilibria and Reactions.—N.m.r. spectroscopy is being increasingly employed to study the mode and course of reactions. Thus n.m.r. has been used to unravel the mechanism of the reaction of phosphorus trichloride and ammonium chloride to give phosphazenes, and to follow the kinetics of alcoholysis of phosphoramidites. Its use in the study of the interaction of nucleotides and enzymes has obtained valuable information on binding sites and conformations and work on the line-widths of the P resonance has enabled the calculation of dissociation rate-constants and activation energies to be performed. 

Work at the Eastern Regional Research Laboratory (35) was concerned with the de-esterification of pectin by two alternative schemes acid and enzyme. It was found that whereas enzyme de-esterification of apple pomace pectin required several minutes, acid de-esterification took 1 to 2 days. Although 40° to 50° C. was optimum for both acid and enzyme de-esterification. 

In summary, therefore, the evidence seems convincing that exercise modifies circulating and tissue concentrations of antioxidants and enzyme activities. It is much less certain that the fatigue or damage to skeletal muscle associated with various forms of excessive or unaccustomed exercise is initiated by free radical-mediated degradation. Considerably more work is required in this area to clarify the underlying pathogenic mechanisms. 

Second, sensors are often intended for a single use, or for usage over periods of one week or less, and enzymes are capable of excellent performance over these time scales, provided that they are maintained in a nfild environment at moderate temperature and with minimal physical stress. Stabilization of enzymes on conducting surfaces over longer periods of time presents a considerable challenge, since enzymes may be subject to denaturation or inactivation. In addition, the need to feed reactants to the biofuel cell means that convection and therefore viscous shear are often present in working fuel cells. Application of shear to a soft material such as a protein-based film can lead to accelerated degradation due to shear stress [Binyamin and Heller, 1999]. However, enzymes on surfaces have been demonstrated to be stable for several months (see below). 

When Murad, Furchgott, and Ignarro received their Nobel Prizes, however, scientists still did not know exactly how nitroglycerin was broken down by the body and converted into nitric oxide. In 2002, researchers at Duke University in North Carolina found an enzyme in mitochondria, the cell s powerhouse, that they believe is responsible for this process. This discovery also explained a phenomenon that doctors had long observed—over time, nitroglycerin stops working and no longer relieves the patient s chest pain. 

Biocatalysts Ltd. works through customer agreements with customer, so far, they already hold exclusivity agreements with some blue chip companies around the world. The R D program is focused on the development of new enzymes and enzyme complexes mainly identified by customers. British Universities undertake most of the needed basic research into new enzymes through allegiances with Biocatalyst Ltd. This allows the in-house scientists to focus onto the customers needs, whilst keeping full up to date with the latest developments in bioresearch. 

For my first volume as Editor, I have invited Professor Colin D. Hubbard (University of Erlangen-Niirnberg, Erlangen, Germany and University of New Hampshire, Durham, NH, USA) as co-editor. Professor Hubbard studied chemistry at the University of Sheffield, and obtained his PhD with Ralph G. Wilkins. Following post-doctoral work at MIT, Cornell University and University of California in Berkeley, he joined the academic staff of the University of New Hampshire, Durham, where he became Professor of Chemistry in 1979. His interests cover the areas of high-pressure chemistry, electron transfer reactions, proton tunnelling and enzyme catalysis. 

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