Other Enzyme Info Flashcards
What is Phosphorylation?
Phosphorylation can activate or inactivate enzymes by causing conformational changes in the protein structure, thereby influencing its activity.
What are the three amino acids that phosphorylation focuses on?
Serine (Ser), Threonine (Thr), and Tyrosine (Tyr)
Where does phosphorylation typically occur?
On the hydroxyl groups of amino acids
Where does the phosphoryl group come from?
The phosphoryl group that is added to the enzyme usually comes from ATP
What are Kinases and Phosphatases?
Kinases are responsible for adding phosphoryl groups to proteins. Phosphatases are responsible for removing phosphoryl groups from proteins, reversing the action of kinases.
What are Zymogens?
Zymogens are inactive enzyme precursors that can be activated by the cutting of specific peptide bonds
Why are Zymogens synthesized in an inactive form?
To prevent premature activity
What are the benefits of Zymogens?
Since they are stored in an inactive form, they can be activated at any time necessary
There is also a cascade effect as when one Zymogen is activated it is more likely for another to be activated
How does Chymotrypsinogen behave as a Zymogen?
Chymotrypsinogen is a single polypeptide chain that is cross-linked by disulfide bonds. The first cleave comes from trypsin and the second comes from itself to turn into chymotrypsin (The active form)
What are the natural substrates for chymotrypsin?
The natural substrates of chymotrypsin are proteins or peptides
What is p-Nitrophenyl acetate?
p-Nitrophenyl acetate is a synthetic substrate commonly used in laboratory studies of chymotrypsin because p-nitrophenyl acetate is hydrolyzed is is yellow
What are the two phases of Chymotrypsin’s reaction?
Acylation Phase: This is the first step, where the substrate binds to the enzyme (C-terminal fragment is produced)
Deacylation Phase: Water attacks the acyl-enzyme intermediate, breaking the bond, and releasing the second product (N-terminal fragment)
What is the catalytic triad of Chymotrypsin?
Serine 195: Nucleophile that attacks the peptide bond. (Nucleophile)
Histidine 57: General acid-base catalyst that activates serine and water (Proton Holder)
Aspartate 102: Stabilizes the histidine, facilitating proton transfers. (Stabalizer)
What are the 6 classes of enzymes?
Oxidoreductases
Transferases
Hydrolases
Lyases
Ligases
Isomerases
What does each class of enzyme catalyze?
Oxidoreductases: Catalyze oxidation-reduction (redox) reactions
Transferases: Transfers functional groups
Hydrolases: Catalyze the hydrolysis of bonds by adding water
Lyases: Catalyze the breaking of bonds
Ligases: Catalyze the joining of two molecules
Isomerases: Catalyze the rearrangement of atoms within a molecule
How are enzymes named?
Enzymes are usually named based on the substrate they act upon and the type of reaction they catalyze. (Often ends in -ase)
What is acid-base catalysis?
Acid-Base Catalysis: Mechanism that involves proton transfer to accelerate a reaction.
What is metal-ion catalysis?
Metal-Ion Catalysis: Involves metal ions acting as Lewis acids to stabilize intermediates or increase nucleophilicity. (Zn, Fe, Mg, and Ca are the most popular ones)
What is the difference between absolute and relative enzyme specificity?
Absolute Specificity: Enzymes act on only one specific substrate.
Relative Specificity: Enzymes act on a range of similar substrates.
What is Stereospecificity?
It is when enzymes are selective for one stereoisomer, which reflects precise substrate binding.
What are Transition State Analogues?
Potent inhibitors that mimic the enzyme’s transition state.
What are Abzymes?
Catalytic antibodies that perform enzymatic reactions, induced by transition state analogues. (Antibodies that act like enzymes)
What are coenzymes?
Coenzymes are small molecules that assist enzymes in catalyzing reactions. They are not proteins themselves but are required for enzyme activity.
What are examples of coenzymes?
Coenzymes can be inorganic metals or organic molecules derived from vitamins.
How is NAD+ a coenzyme?
It participates in reactions where it acts as an electron carrier, accepting electrons during oxidation reactions to become NADH.
What makes up the structure of NAD+?
Nicotinamide ring: The site of redox activity, where electrons are transferred
Adenine ring: Part of the nucleotide structure.
Two sugar-phosphates: These link the nicotinamide and adenine portions, forming a dinucleotide.
What is important about B6 vitamins?
B6 vitamins participate in amino acid biosynthesis
What is an Apoenzyme?
It’s an inactive form of an enzyme that requires a cofactor to become a holoenzyme (the active version of an epoenzyme)
