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The active site of an enzyme
Enzyme

Enzymes are biomolecules that catalysis chemical reactions. Almost all enzymes are proteins. In enzymatic reactions, the molecules at the beginning of the process are called Substrate , and the enzyme converts them into different molecules, the products....
 contains the catalytic
Catalysis

Catalysis is the process in which the reaction rate of a chemical reaction is either increased or decreased by means of a chemical substance known as a catalyst....
 and binding sites. The structure and chemical properties of the active site allow the recognition and binding of the substrate
Substrate (biochemistry)

In biochemistry, a substrate is a molecule upon which an enzyme acts. Enzymes catalysis chemical reactions involving the substrate. The substrate binds with the enzyme active site, and an enzyme-substrate complex is formed....
.

The active site is usually a big pocket at the surface of the enzyme that contains residues responsible for the substrate specificity (charge, hydrophobicity, steric hindrance) and catalytic residues which often act as proton donors or acceptors or are responsible for binding a cofactor such as PLP, TPP
Thiamine pyrophosphate

Thiamine pyrophosphate , or thiamine diphosphate , is a thiamine Derivative which is produced by the enzyme thiamine pyrophosphatase. Thiamine pyrophosphate is a coenzyme that is present in all living systems, in which it catalyzes several Biochemistry reactions....
 or NAD.






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Encyclopedia


The active site of an enzyme
Enzyme

Enzymes are biomolecules that catalysis chemical reactions. Almost all enzymes are proteins. In enzymatic reactions, the molecules at the beginning of the process are called Substrate , and the enzyme converts them into different molecules, the products....
 contains the catalytic
Catalysis

Catalysis is the process in which the reaction rate of a chemical reaction is either increased or decreased by means of a chemical substance known as a catalyst....
 and binding sites. The structure and chemical properties of the active site allow the recognition and binding of the substrate
Substrate (biochemistry)

In biochemistry, a substrate is a molecule upon which an enzyme acts. Enzymes catalysis chemical reactions involving the substrate. The substrate binds with the enzyme active site, and an enzyme-substrate complex is formed....
.

The active site is usually a big pocket at the surface of the enzyme that contains residues responsible for the substrate specificity (charge, hydrophobicity, steric hindrance) and catalytic residues which often act as proton donors or acceptors or are responsible for binding a cofactor such as PLP, TPP
Thiamine pyrophosphate

Thiamine pyrophosphate , or thiamine diphosphate , is a thiamine Derivative which is produced by the enzyme thiamine pyrophosphatase. Thiamine pyrophosphate is a coenzyme that is present in all living systems, in which it catalyzes several Biochemistry reactions....
 or NAD. The active site is also the site of inhibition of enzymes (see Enzyme inhibitor
Enzyme inhibitor

Enzyme inhibitors are molecules that bind to enzymes and decrease their enzyme activity. Since blocking an enzyme's activity can kill a pathogen or correct a metabolism imbalance, many drugs are enzyme inhibitors....
 article).

Models

There are two proposed models of how enzymes work: the lock-and-key model and the induced fit
Enzyme catalysis

Enzyme catalysis is the catalysis of chemical reactions by specialized proteins known as enzymes. Catalysis of biochemical reactions in the cell is vital due to the very low reaction rates of the uncatalysed reactions....
 model. The lock-and-key model assumes that the active site is a perfect fit for a specific substrate and that once the substrate binds to the enzyme no further modification is necessary, this is simplistic. The induced fit model is a development of the lock and key model and instead assumes that an active site is more flexible and that the presence of certain residues (amino acids) in the active site will encourage the enzyme to locate the correct substrate, after which conformational changes may occur as the substrate is bound.

Substrates bind to the active site of the enzyme or a specificity pocket through hydrogen bonds, hydrophobic interactions, temporary covalent bonds (van der waals) or a combination of all of these to form the enzyme-substrate complex. Residues of the active site will act as donors or acceptors of protons or other groups on the substrate to facilitate the reaction. In other words, the active site modifies the reaction mechanism in order to decrease the activation energy of the reaction. The product is usually unstable in the active site due to steric hindrances that force it to be released and return the enzyme to its initial unbound state.

See also

  • Enzyme catalysis
    Enzyme catalysis

    Enzyme catalysis is the catalysis of chemical reactions by specialized proteins known as enzymes. Catalysis of biochemical reactions in the cell is vital due to the very low reaction rates of the uncatalysed reactions....
  • Hugh Stott Taylor
    Hugh Stott Taylor

    Hugh Stott Taylor was an English chemist primarily interested in catalysis. In 1928, in a landmark contribution to catalytic theory, Taylor suggested that a catalyzed chemical reaction is not catalyzed over the entire solid surface of the catalyst but only at certain ?active sites? or centers....
  • Catalytic triad
    Catalytic triad

    A catalytic triad commonly refers to the three amino acid residues found inside the active site of certain protease enzymes: serine , aspartate and histidine ....
  • Activity based proteomics
    Activity based proteomics

    Activity based proteomics, or activity based protein profiling is a functional proteomics technology that uses specially designed chemical probes that react with mechanistically-related classes of enzymes....