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Catalytic Antibodies: New Tool for Molecular Biology
| Article
# : |
13873 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
12 / 1988 |
3,151 Words |
| Author
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Rudy M. Baum
Rudy M. Baum is the West Coast bureau head of the weekly
newsmagazine Chemical & Engineering News. |
Antibodies represent one of the immune system's fundamental weapons against external invaders, including bacteria, viruses, and protein toxins. Enzymes, by contrast, are biology's catalysts, complex molecules that dramatically increase the rate of important biochemical reactions. Although their functions differ, antibodies and enzymes are both protein molecules. Both antibodies and enzymes are vitally important in maintaining the health of an individual.
A number of researchers are exploring ways to introduce the catalytic activity of enzymes into antibody molecules. Initial successes in creating such "catalytic antibodies" have demonstrated that such a marriage is feasible. Continuing efforts to expand the types of reactions such molecules can catalyze hold the promise of a better understanding of protein function, new tools for research in molecular biology, and powerful new pharmaceuticals.
Biochemists have known for many years that a fundamental similarity exists between antibodies and enzymes, but that they are also quite different. Antibodies bind for the sake of binding. They perform their duties by recognizing molecules foreign to the body and attaching to them. In doing so, the antibody tags the invading molecule—in immunological terms, an antigen—as foreign, which allows the body to eliminate it.
Enzymes, on the other hand, bind to facilitate a chemical reaction. They perform this task throughout the plant and animal worlds, with a single mammalian cell containing an average of about 3,000 different enzymes. Among the multitude of biochemical reactions that are vital to the health of the organism, many could never occur under the temperature and pressure conditions in the body unless a suitable enzyme is present to facilitate each reaction.
Reactions between molecules or atoms occur spontaneously only when the products of the reaction have a lower energy than the original reactants. This "thermodynamic" consideration determines whether or not a reaction is feasible. For example, two molecules of water, H2O, have lower energy than the original reactants: two molecules of hydrogen, H2, and one molecule of oxygen, O2. Thus the reaction is thermodynamically permitted. In fact, under the right circumstances hydrogen and oxygen combine explosively, with the energy released representing the difference between the free energy of the reactants and products.
Nevertheless, a bottle full of H2 and O2 could sit placidly for years
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