How Enzymes Work

Enzymes are proteins that consist of sequences of amino acids gathered together by peptide bonds. An enzyme molecule can have one or more peptide bond or polypeptide chains. The sequence of amino acids inside the polypeptide chains is specific for each enzyme and is thought to establish the unique three-dimensional structure in which the chains are composed.

This conformation, which is essential for the functionality of the enzyme, is stabilized by interactions of amino acids in several zones of the peptide chains with each other and with the nearby medium. These interactions are relatively weak and can be disrupted quickly by high temperatures, acid or alkaline ambience, or changes in the polarity of the medium. Such changes lead to an unfolding of the peptide chains (or denaturation) and a subsequent loss of enzymatic activity, solubility, and other abilities characteristic of the native enzyme.

Many enzymes have an additional, nonprotein component, called a coenzyme. This can be an organic molecule, often a vitamin by-product, a metal ion (copper and zinc for some of the enzymes in snail mucins) or an organic (usually metal-containing) group.

The coenzyme, in most cases, participates directly in the catalytic reaction. For example, it can act as an intermediate carrier of a group being carried from one substrate to another. Certain enzymes have coenzymes that are strongly linked to the protein and difficult to remove, while others have coenzymes that dissociate quickly. When the protein unit and the coenzyme are separated from each other, neither possesses the catalytic abilities of the former conjugated protein (the holoenzyme).

By simply mixing the protein unit and the coenzyme together, the completely active holoenzyme can usually be reconstituted. The same coenzyme can be associated with many enzymes which catalyze different activities. It is thus mainly the nature of the protein unit rather than that of the coenzyme which commands the specificity of the reaction.

The enzyme-cofactor couple confers an active configuration, usually including an active site into which the substance (substrate) involved in the reaction can fit. Many enzymes are specific to one substrate. If a competing molecule occupies the active site or alters its shape, the enzyme's action is inhibited. If the enzyme's composition is altered its activity is lost.

Enzymes are classified by the kind of reaction they catalyze: (1) oxidation-reduction, (2) change of a chemical group, (3) hydrolysis, (4) elimination or addition of a chemical radical, (5) isomerization, and (6) joining together of substrate units (polymerization).

Enzymes catalyze all aspects of cell metabolism, including the digestion of aliments, in which large nutrient molecules (including proteins, carbohydrates, and fats) are divided into tinier molecules; the conservation and transformation of chemical energy; and the creation of cellular elements and components.

The fermentation of wine, leavening of bread, curdling of milk into cheese, and brewing of beer are all enzymatic reactions. The uses of enzymes in medicine involve destroying disease-causing microorganisms, the treatment of wounds, and diagnosing certain diseases.

Thanks to enzymatic processes, science has been able to derive new treatments that can help repair damaged skin.

A new skin moisturizer offers the chance to get rid of scars, imperfections and several skin ailments thanks to a natural ingredient that repairs damaged tissue.

- Kathleen LeRoi