Enzyme Kinetics Flashcards
(44 cards)
Define: Catalyst
Increases the rate of reaction by decreasing the energy barrier
Why are enzymes a special type of catalyst?
- They can increase the rate by 106 to 1012 greater than non-catalyst reactions, and 103 increase greater than non-enzymatic catalysts.
- Can occur in mild conditions (pH 7, >100C°, 1atm)
- Can be regulated by biologcial molecules
Unit (when measuring ezymic activity)
Amount of substrate converted to product in a given time (ex: 1µmol/min)
Specific Activity
Number of units per a mg of protein
Temperature optimum: definition and average for humans
The temperature at which ezymes perform the best. Typically 37C° for humans
pH optimum for pepsin
pH of 2
pH optimum of Trypsin
pH of 8
Oxidoreductases
Catalyze reduction-oxidation reactions
Transferases
Catalyses the transfer of a group (glycosyl, methyl, phosporyl)
Hydrolases
Catalyzes hydrolytic cleavage of bonds
(C-C, C-O, C-N, and others)
Lyases
Catayzes atom elimination to leave double bonds
(C-C, C-O, C-N, and others)
Isomerases
Catalyses geometric/structural changes in a molecule
Ligases
Catalyzes the joining of 2 molecules.
Coupled to hydrolysis of ATP
Active Site
Specific region on the enzyme where the catalysis occurs. Substrates bind to the active site (plus any required elements) in a specific manor. Enzyme structure determines active site structure, so changes in structure may (or may not) affects the active site.
Catalysis by proximity
Molecules must come within bond forming distance. Active sites create a high local concentration of the target molcule by binding it. Substrates are bound in a specific orientation conducive to the reaction.
Acid-Base Catalysis
Ionizable functional groups of amino acids may act as an acid or base in the catalysis
Catalysis by strain
If catalyzing reaction is to break bonds, the substrates may be bound in such a way that the bonds are destabilized.
Covalent Catalysis
The enzyme and substrate covalently bond. The modified enzyme becomes the subtrate for a different reaction.
Keq of the modified enzyme > Keq of the inital substrate to the product
Prostetic groups
Tightly/stably incorporated into the proteins (sometimes by covalent bonds). Metal ions are the most common.
Most common metal prostetic groups
Co, Cu, Mg, Mn, Zn
Cofactors
Bind transiently to the substrate or enzyme, but are required for activity
Metalloenzymes
Enzymes that contain a metal prostetic group
Coenzymes
Accept a group from one reaction, and supplies groups in other reactions
Ex: CoA transfers acyl groups, Folates transfer 1 carbon groups
Isoenzymes
Physically different enzymes that catalyze the same reaction. May have different properties like substrate affinities or activity regulation. May be expressed differently by different tissues.

