Enzyme Kinetics II

Flashcards covering catalytic mechanisms, enzyme regulation, allostery, and enzyme inhibition.

Catalysis by Approximation

When there is more than one substrate, proximity and orientation can substantially enhance the rate of reaction.

Covalent Catalysis

Enzyme active site contains a reactive group that allows the substrate to become temporarily covalently bound to enzyme through nucleophilic attack. This temporary covalent bond stabilizes the transition state, lowering the activation energy required for the reaction to proceed.

General Acid-Base Catalysis

Using a proton donor (acid) or acceptor (base) other than water to stabilize the transition state.

Chymotrypsin

A protease found in the gut that demonstrates covalent catalysis and general acid-base catalysis properties.

Catalytic Triad

Specifically orientated aspartate, histidine and serine residues in the active site of chymotrypsin.

Oxyanion Hole

Structure in the active site of chymotrypsin made of peptide NH groups of active site residues that helps stabilize the tetrahedral transition state intermediate.

Metal Ion Catalysis

Enzymes utilize metal ions for parts of their catalytic mechanisms for oxidation/reduction, electrophilic catalysis, or to bind water for nucleophilic attack.

Enzyme Regulation

Control of enzyme activity through compartmentalization, substrate/product amount, enzyme amount, post-translational modifications, cofactors, activators, inhibitors, or enzyme specificity/affinity.

Apoenzyme

Enzyme without its cofactor.

Holoenzyme

Apoenzyme + cofactor.

Post-translational modification

Chemical modifications to a protein after translation, such as proteolytic cleavage, phosphorylation, acetylation, ubiquitination, etc.

Ubiquitination

Post-translational modification involving the addition of ubiquitin to target proteins, often targeting them for degradation.

Phosphorylation

Post-translational modification involving the addition of phosphate groups to specific residues (serine, threonine, tyrosine) by kinases.

Allostery

Regulation of an enzyme by binding an effector molecule at a site other than the enzyme's active site.

Allosteric Enzymes

Enzymes with multiple active sites that often show cooperativity.

Allosteric Activators

Molecules that bind to an enzyme and increase its activity.

Allosteric Inhibitors

Molecules that bind to an enzyme and decrease its activity.

Competitive Inhibitors

Inhibitors that bind to the active site of an enzyme, competing with the substrate.

Non-Competitive Inhibitors

Inhibitors that bind to an enzyme at a site other than the active site, stopping the enzyme from working.

Uncompetitive Inhibitors

Inhibitors that bind only to the enzyme-substrate (ES) complex.

Chymotrypsin catalytic mechanism

Substrate binding, Nucleophilic attack, Tetrahedral intermediate collapse, amine component release, water binding, nucleophilic attack, tetrahedral intermediate collapse, carboxyclic acid component release