any of various proteins, formed in plant and animal cells or made synthetically, that act as organic catalysts in initiating or speeding up specific chemical reactions and that usually become inactive or unstable above c. 50°C (122°F)
Ger enzym < LGr enzymos, leavened < Gr en-, in + zymē, leaven (see zyme)
A proteinmolecule that helps other organic molecules (see also organic molecule) enter into chemical reactions with one another but is itself unaffected by these reactions. In other words, enzymes act as catalysts for organic biochemical reactions.
Any of numerous proteins produced in living cells that accelerate or catalyze the metabolic processes of an organism. Enzymes are usually very selective in the molecules that they act upon, called substrates, often reacting with only a single substrate. The substrate binds to the enzyme at a location called the active site just before the reaction catalyzed by the enzyme takes place. Enzymes can speed up chemical reactions by up to a millionfold, but only function within a narrow temperature and pH range, outside of which they can lose their structure and become denatured. Enzymes are involved in such processes as the breaking down of the large protein, starch, and fat molecules in food into smaller molecules during digestion, the joining together of nucleotides into strands of DNA, and the addition of a phosphate group to ADP to form ATP. The names of enzymes usually end in the suffix -ase.