What are Enzymes?

Reactant are complex macromolecules that act as catalysts for biochemical reactions in living organisms. They are composed of amino acids joined together to form long chains known as polypeptides. Once reactant are synthesized in cells, they fold into intricate three-dimensional structures that are perfectly suited to interact with specific substrate molecules and accelerate the chemical reactions they undergo. 

Enzyme Structure and Enzymes

The 3D structure of an enzyme is directly related to its function. At the core of the Enzymes is an active site - a pocket or cleft that binds to the substrate. Residues lining the active site form weak interactions with functional groups on the substrate to hold it in position for catalysis. Nearby are catalytic residues that donate or accept electrons to lower the activation energy of reactions. Substrate binding induces a conformational change that perfects the active site geometry for catalysis.

Catalytic Mechanisms

Most reactant utilize one of four general catalytic mechanisms: acid/base catalysis, nucleophilic catalysis, covalent catalysis and metal ion catalysis. In acid/base catalysis, enzyme residues donate or accept protons from substrates to facilitate addition or removal reactions. Nucleophilic catalysis involves the active site attacking electrophilic centers on substrates. Some reactant form covalent intermediates with substrates via acyl-enzyme or glycosyl-enzyme intermediates. Metalloreactant require divalent metal cations like zinc or magnesium in their active sites to polarize bonds for catalysis.

Regulation of Enzyme Activity

Cells regulate enzyme activity through various allosteric and covalent modifications. Allosteric reactant contain regulatory sites distinct from the active site. Binding of allosteric effectors induces conformational shifts that increase or decrease the enzyme's affinity for its substrate. Post-translational modifications like phosphorylation can mask or expose the active site, altering catalytic efficiency. Proteolysis activates or inactivates zymogens through selective cleavage of propeptide regions.

Get More Insights on- Enzymes