What is "enzyme"

enzyme \en"zyme\ ([e^]n"z[imac]m), n. [Pref. en- (Gr. 'en in) + Gr. zy`mh leaven.] (Physiol. Chem.) A protein produced by a living organism, capable of catalyzing a chemical reaction. Almost all processes in living organisms require some form of enzyme to cause the reactions to occur at a rate sufficient to support life. There are a very wide variety of enzymes, each specifically catalyzing a different chemical reaction, the sum of which cause the bulk of the physiological changes observed as life processes. Enzymes, like most proteins, are synthesized by the protein-synthetic mechanism of the living cell, at special sites on ribosomes, using the genetic information in messenger RNA transcribed from the genetic instructions stored as nuleotide sequences in the DNA (or in some viruses, the RNA) of the genome. Some examples of enzymes are: pepsin, diastase, rennet, DNA polymerase, invertase, glucose oxidase, protease, and ribonuclease. There are many other types of enzyme.

Note: The 1913 Webster defined an enzyme as: An unorganized or unformed ferment, in distinction from an organized or living ferment; a soluble, or chemical, ferment.

1881, as a biochemical term, from German Enzym, coined 1878 by German physiologist Wilhelm Kühne (1837-1900), from Modern Greek enzymos "leavened," from en "in" (see en- (2)) + zyme "leaven" (see zymurgy). Related: Enzymotic.

n. (context biochemistry English) A globular protein that catalysis a biological chemical reaction.

n. any of several complex proteins that are produced by cells and act as catalysts in specific biochemical reactions

Enzymes are macromolecular biological catalysts. Enzymes accelerate, or catalyze, chemical reactions. The molecules at the beginning of the process upon which enzymes may act are called substrates and the enzyme converts these into different molecules, called products. Almost all metabolic processes in the cell need enzymes in order to occur at rates fast enough to sustain life. The set of enzymes made in a cell determines which metabolic pathways occur in that cell. The study of enzymes is called enzymology.

Enzymes are known to catalyze more than 5,000 biochemical reaction types. Most enzymes are proteins, although a few are catalytic RNA molecules. Enzymes' specificity comes from their unique three-dimensional structures.

Like all catalysts, enzymes increase the rate of a reaction by lowering its activation energy. Some enzymes can make their conversion of substrate to product occur many millions of times faster. An extreme example is orotidine 5'-phosphate decarboxylase, which allows a reaction that would otherwise take millions of years to occur in milliseconds. Chemically, enzymes are like any catalyst and are not consumed in chemical reactions, nor do they alter the equilibrium of a reaction. Enzymes differ from most other catalysts by being much more specific. Enzyme activity can be affected by other molecules: inhibitors are molecules that decrease enzyme activity, and activators are molecules that increase activity. Many drugs and poisons are enzyme inhibitors. An enzyme's activity decreases markedly outside its optimal temperature and pH.

Some enzymes are used commercially, for example, in the synthesis of antibiotics. Some household products use enzymes to speed up chemical reactions: enzymes in biological washing powders break down protein, starch or fat stains on clothes, and enzymes in meat tenderizer break down proteins into smaller molecules, making the meat easier to chew.