BIO NMDCAT

A mutation in the small number of residues forming the active site would directly abolish enzyme function, unlike mutations in distant structural or surface regions.

Turnover number represents the maximum number of chemical conversions of substrate molecules per second that a single catalytic site executes.

The complete, active enzyme (holoenzyme) consists of the protein part (apoenzyme) and a cofactor. Removing the cofactor leaves the inactive apoenzyme.

Feedback inhibition is a regulatory mechanism where the end product of a pathway inhibits an enzyme acting earlier, preventing overproduction.

Enzymes accelerate reactions by stabilizing the transition state and providing an alternative reaction pathway with a lower activation energy.

At saturating substrate concentrations, the reaction rate is limited by enzyme concentration. Increasing the amount of enzyme creates more active sites and increases Vmax.

Enzyme specificity results from the chemical complementarity between the active site and the substrate's transition state.

Km is the substrate concentration at half of Vmax. A low Km indicates high affinity, requiring only a low concentration to reach effective catalytic rates.

Unlike inorganic catalysts, enzymes are highly specific and their activity is finely regulated by cellular mechanisms like allosteric control.

By lowering the activation energy, enzymes allow a much larger proportion of substrate molecules to reach the transition state at a given temperature, increasing the reaction rate.

The protein portion alone is the inactive apoenzyme, which requires a non-protein cofactor to form the complete, active holoenzyme.

Enzyme specificity arises from the unique 3D structure of the active site, which contains amino acid R-groups positioned to form interactions only with a specific substrate.

The induced fit model is exemplified by conformational changes in hexokinase upon glucose binding, which correctly orient ATP for catalysis.

Absolute specificity means the enzyme acts on only one specific substrate, unlike group specificity which acts on substrates with a common functional group.

DNA polymerase catalyzes the template-directed addition of deoxynucleotides to a growing DNA chain.

Isoenzymes are multiple forms of an enzyme that catalyze the same reaction but differ in kinetic properties, allowing for tissue-specific metabolic tailoring.

Many coenzymes are vitamin derivatives, such as pyridoxal phosphate (vitamin B6) which is required for aminotransferases.

Substrate binding is mediated by multiple weak, non-covalent forces which are reversible, essential for both binding and product release.

A coenzyme is a non-protein organic molecule that binds transiently to an apoenzyme, allowing it to be separated by dialysis, unlike a prosthetic group.