Lecture 9.29.14 (Ch.9 Enzyme Catalysis) Flashcards
Acidic Residue
Neutral to Negative
Acidic Residue want charge…
pka decrease
Acidic Residue not want charge
pka increase
catalytic residue (4)
amino acid side chain in the active site that is involved in:
- mechanism
- altering the pka of a residue
- weakens covalent bonds
- stabilize transition state
Basic Residue
Charged to Neutral
Basic Residue want charge….
pka increase
Basic Residue not want charge…
pka decrease
Nucleophile
nucleus loving
has extra electrons
atoms with lone pairs
Electrophile
electron loving
has lack of electrons
atoms with plus charge
proteases
enzymes that hydrolyze peptide bonds
Strategies used for enzyme catalysis
covalent catalysis
acid-base catalysis
covalent cataylsis
the active site contains a reactive group, usually a nucleophile, that becomes temporarily covalently attached to part of a substrate
ex. chymotrypsin
acid-base catalysis
a molecule other than water plays the role of a proton donor or acceptor
chymotrypsin cleaves peptide bonds from the ______?
carboxyl terminal side of large hydrophobic amino acids
which amino acids are cleaved by chymotrypsin?
tryptophan, tyrosine, phenylalanine, methionine, and leucine
which residue plays a central role in the mechanism of chymotrypsin?
serine residue
What are the 2 phase of chymotrypsin hydrolysis?
- Acylation to form the acyl-enzyme intermediate followed by
- deacylation to regenerate the free enzyme
Types of proteases? (4)
serine
metallo
cystetine/thiol
acid/aspartic
A basic amino acid is always acting like an
ACID
An acid amino acid is always acting like a
BASE
Acid
H+ donor, electron acceptor
Base
H+ acceptor, electron donor
Metallo proteases
metal(Zn) activates electrophile
Carboxypeptidase A (CPA) cuts off
C terminal residue
ex. AFRIDAY-> AFRIDA & Y
CPA needs ______ to function and fold
Zn+2 (as acts an acid)
What type of intermediate in involved in CPA?
tetrahedral
Typsin cleaves
Bases
Lysine and Arginine
Elastase cleaves
No polar aliphatic
Glycine and Alanine
