Catalytic Triad
This residue acts as the base that removes a proton from serine, making it a stronger nucleophile.
What is Histidine?
Chymotrypsin belongs to this enzyme family that cleaves peptide bonds.
What are Proteases?
In the RNase A mechanism shown, this type of catalysis occurs when positively charged residues stabilize the negatively charged phosphate group.
What is Electrostatic Catalysis?
This catalytic strategy occurs when an enzyme removes a proton to create a stronger nucleophile.
What is Base Catalysis?
Enzymes that break bonds using water are called these.
What are Hydrolases?
This residue stabilizes the positive charge on histidine and properly orients it within the active site.
What is Aspartate?
In many steps of the chymotrypsin mechanism, histidine uses this enzyme mechanism to let go of a proton, to create a leaving group.
What is Acid Catalysis?
In step 1 of the diagram, this histidine residue acts as a base by removing a proton from the 2′-OH, creating a strong nucleophile.
What is His12?
When an enzyme donates a proton to create a better leaving group, it is using this mechanism.
What is Acid Catalysis?
Enzymes that remove groups to form double bonds fall under this category.
What are Lyases?
The last step of the catalytic triad involves this nucleophile attacking the substrate after deprotonation.
What is Serine?
The substrate side chains fit into this nonpolar region that determines specificity.
What is the Hydrophobic Pocket?
The nucleophilic attack initiated by the 2′-OH produces this specific intermediate shown at the top of the figure.
What is a 2′,3′-cyclic nucleotide (cyclic phosphate) intermediate?
This form of catalysis involves forming a temporary covalent bond between enzyme and substrate.
What is Covalent Catalysis?
Enzymes that transfer functional groups between molecules belong to this class.
What are Transferases?
The primary chemical effect of the catalytic triad is increasing the nucleophilicity of this functional group on serine.
What is the Hydroxyl Group?
The negatively charged oxygen in the intermediate is stabilized in this region of the enzyme.
What is the Oxyanion Hole?
During formation of the cyclic intermediate, this histidine donates a proton to facilitate departure of the leaving group, demonstrating acid catalysis.
What is His119?
Hydrogen bonds and charge interactions that stabilize a transition state are examples of this catalytic method.
What is Electrostatic Catalysis?
This class catalyzes intramolecular rearrangements.
What are Isomerases?
The key interaction that allows the catalytic triad to function efficiently is this type of charge-stabilizing interaction.
What is Salt Bridge?
After the acyl-enzyme forms, this molecule is activated by histidine to attack the carbonyl and release the second product.
What is Water?
In step 2 of the RNase A mechanism, the two histidines switch roles so that water can attack the cyclic intermediate; this overall strategy is known as this enzyme mechanism.
What is General Acid–Base Catalysis?
Designing a drug that mimics this structure often produces the strongest enzyme inhibitors because enzymes bind it most tightly.
What is the Transition State?
Acid hydrolases found in lysosomes function best in environments with this characteristic.
What is Low pH (Acidic Conditions)?