Chapter 9 Flashcards
What is binding Energy?
Binding energy is the free energy released in the formation of a large number of weak interactions between the enzyme and substare. Free energy released by substrate binding to active site (ES).
Icrease substrate specificity
Increase in Catalytic efficiency
What are the different catalytic strategies?
- Colvalent Catalysis: Active site has a reactive functional group that is temporarily covalently attached to a part of the substrate in the course of catalysis. (covalently modified) and example would be chymotrpisin
- General Acid-Base Catalysis: A molecule other than water acts as a proton donor or acceptor. (i.e. chycotrpisin)
- Metal Ion Catalysis: Stabilize charge at active site, generation of nucleophiles
- _ Catalysis by approximation: _The substrates are brought closely together to facilitate the reaction.
What are the three major type of enzymes?
Serine Proteases
Cystein Proteases
Aspartyl proteases
What is serine protease-chymotrpsin?
It cleaves peptide bonds selectively on the carboxyl terminal side of the large hydrophobic amino aicds.
In addition to breaking down peptide bonds, some proteases can act on substrates
There are two phases?
- Acylation Phase (associated with this) and the burst phase. Acyl group of the substrate becomes covalently attached to the enzyme as the yellow product is released. It forms an acyl enzyme intermediate
- Deacylation phase in the presence of water molecule steady state phase
What is DIPF?
DIPF is a group of specific inhibitor it modifies the OH group but it only binds to Ser 195.
Enzyme was treated with DIF and the group was a specific inhibitor adn reacts with speicifc functional groups
What is the Catalytic Triad?
Key players in reaction mechanism
SErine is part of a catalytic triad that also includes histidine and asparate
Serine has an OH and is involved in acylation
Hisitidine starts out neutral, acts as a proton donor
Aspartate helps stabilize imidazole ring on hisitidine
What is the reaction mechanism?
Two tetrahedral intermediates form and an oxyanion hole. Three acyl enzymes
What is Double displacement reaction?
Colvent catalysis and general acid base catalysis
The oxyanion Hold is part of the acitve site.
The structure stabilizes the tetrahedral intermediate of the chemotrpsin reaction.
Note: hydrogen bonds link peptide NH groups adn teh negatively charged oxygen atom of teh intermediate
If i mutated the protein and altered the amino acids that form the oxyanion hole, which of the folling woudl i be.
What is the S2 hydrophobic pocket
It helps with specifity
There is a pocket in which a side chain can fit
Describe serine proteases
catalytic triad
secreted by the panceras zymogens
DIPF are reacted with this similar mechanisms of actions
Chymotrypsin involves amino acids with aromatic rings the S1 poket is hydrophobic
Tyrpsin has a positively charged side chain
substrate will ahve a positive charge and the negative charge
