Many therapeutic drugs and poisons are enzyme inhibitors. Enzyme activity can be affected by other molecules: inhibitors are molecules that decrease enzyme activity, and activators are molecules that increase activity. Enzymes differ from most other catalysts by being much more specific. Chemically, enzymes are like any catalyst and are not consumed in chemical reactions, nor do they alter the equilibrium of a reaction. An extreme example is orotidine 5'-phosphate decarboxylase, which allows a reaction that would otherwise take millions of years to occur in milliseconds. Some enzymes can make their conversion of substrate to product occur many millions of times faster. Like all catalysts, enzymes increase the reaction rate by lowering its activation energy. Enzymes' specificity comes from their unique three-dimensional structures. Other biocatalysts are catalytic RNA molecules, called ribozymes. Įnzymes are known to catalyze more than 5,000 biochemical reaction types. The study of enzymes is called enzymology and the field of pseudoenzyme analysis recognizes that during evolution, some enzymes have lost the ability to carry out biological catalysis, which is often reflected in their amino acid sequences and unusual 'pseudocatalytic' properties. : 8.1 Metabolic pathways depend upon enzymes to catalyze individual steps.
Almost all metabolic processes in the cell need enzyme catalysis in order to occur at rates fast enough to sustain life.
The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. Enzymes ( / ˈ ɛ n z aɪ m z/) are proteins that act as biological catalysts by accelerating chemical reactions.
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