**Historical Development**:
– Anselme Payen discovered diastase in 1833.
– Louis Pasteur linked fermentation to vital force in yeast cells.
– Wilhelm Kühne coined the term ‘enzyme’ in 1877.
– Eduard Buchner studied yeast extracts in 1897.
– James B. Sumner crystallized urease and catalase in the 1920s.
**Classification and Nomenclature**:
– Enzymes named based on substrate or reaction catalyzed.
– Examples include lactase, alcohol dehydrogenase, and DNA polymerase.
– Isozymes are different enzymes catalyzing the same reaction.
– Enzyme nomenclature includes EC numbers.
– EC numbers classify enzymes into broad categories based on mechanism.
**Function and Properties**:
– Enzymes accelerate chemical reactions by lowering activation energy.
– Specificity of enzymes comes from their unique three-dimensional structure.
– Enzymes are not consumed in reactions and do not alter equilibrium.
– Enzyme activity can be affected by inhibitors and activators.
– Enzymes catalyze over 5,000 biochemical reaction types.
– Therapeutic drugs and poisons can act as enzyme inhibitors.
**Structural Analysis and Mechanisms**:
– Discovery that enzymes can be crystallized allowed for structural analysis.
– X-ray crystallography used to determine enzyme structures.
– Efforts to understand enzyme function at an atomic level.
– Enzymes bind substrates with specificity through complementary pockets.
– Proofreading mechanisms ensure high accuracy in reactions.
– Lock and key model explains enzyme-substrate specificity.
**Catalysis, Dynamics, and Modulation**:
– Enzymes accelerate reactions by lowering activation energy.
– Enzymes exhibit complex internal dynamic motions.
– Allosteric modulation can inhibit or activate enzymes.
– Some enzymes require cofactors for full activity.
– Enzymes stabilize transition states to reduce energy requirements.
– Enzyme kinetics are essential for understanding enzyme function.
Enzymes (/ˈɛnzaɪmz/) are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. Almost all metabolic processes in the cell need enzyme catalysis in order to occur at rates fast enough to sustain life. Metabolic pathways depend upon enzymes to catalyze individual steps. 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.
Enzymes are known to catalyze more than 5,000 biochemical reaction types. Other biocatalysts are catalytic RNA molecules, called ribozymes. An enzyme's specificity comes from its unique three-dimensional structure.
Like all catalysts, enzymes increase the reaction rate 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 therapeutic drugs and poisons are enzyme inhibitors. An enzyme's activity decreases markedly outside its optimal temperature and pH, and many enzymes are (permanently) denatured when exposed to excessive heat, losing their structure and catalytic properties.
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.