Classes Of Enzymes And Chemotrypsin Flashcards
What is an ec number
Enzyme commission number Tell us which of the 7 classes the enzyme belongs to
Classes are assigned based on the type of reaction it catalyzes
What are the 7 enzyme classes
Oxidoreductase
Transferase
Hydrolase
Lyase
Isomerase
Ligase
Translocase
What does oxidoreductase do and what is an example of one
It does oxidation reduction reactions (transfers electrons)
Ex lactate dehydrogenase NAD+ to NAD
What does transferase do and what is an example of one
Transfers functional groups between molecules
Amino transferase
What does hydrolase do and what is an example of one
- Cleave molecules by addiction of water
Trypsin
What does lyase do and what is an example of one
- Adds atoms or functional groups to double bonds or removes them to form double bonds
Fumarase
What does isomerase do and what is an example of one
- Moves functional groups within one molecule
Proline racemase
What does ligase do and what is an example of one
- Joins two molecules together (powered by atp hydrolysis)
DNA ligase
What does translocase do and what is an example of one
- Catalyzes movement of ions or molecules across membranes or catalyzes their separation within membranes
Sodium potassium pump
Carbonic anhydrase is a
Hexokinase is a
Lyase
Transferase
What is chemotrypsin
Hydrolyzes dietary protiens into small peptides and amino acids (break the peptide bond) so they can be absorbed by the small instestine
Cleaves the carboxy teminal end of large hydrophobic side chains.
What amino acids do chemotrypsin cleave after
Phenylalanine, Methionine, tryptophan, isoleucine, tyrosine
What is the hydrophobic specificity pocket on chemotrypsin
The hydrophobic substrate going in and the peptide bond the needs to be broken is sticking out
The caralytic triad of aA residue of the enzyme cleave the peptide bond
What are the three aA in the catalytic triad
Asp 102
His 57
Ser 195
What does asp 102 do
It orients the his 57 side chain through h bonding interactions and electrostatic effects
Increases the pka of His 57 so it becomes a better base
What does his 57 do
Acts as a base to accept a proton from ser 195 to make it a nucleophile
What does ser 195 do
The deprotonated oxygen on its side chain acts as a nucleophile
What is step one of hydrolysisi by chemtrypsin
The substrate binds to the active site
What is step 2 of hydrolysis by chemotrypsin
His 57 acts as a base and deprotonated ser 195 to make a nuceleophile
Then the serine attacked the polypeptides c=o (carbonyl group)
This makes a tetrahedral intermediate that is unstable so the oxyanion hole (part of the enzyme) sheilds the negative charge on that intermediate
How does the oxyanion hole stablize the negative tetrahedral intermediate
The enzyme wraps around the negative o group of the peptide and the ser 195 and gly 193 residues have nh (amide) groups that do h bonding to the oxygen and stablize it
What is step 3 of hydrolysis by chemotrypsin
The peptide bond in the polypeptide that’s attached to serine 195 breaks (between the carboxy and n terminus) this collapses the tetrahedral intermediate
This is covalent catalysis
His 57 acts as an acid and give a proton to the lone pair on the newly broken NH terminus to make NH2-R2
This forms the acyl enzyme
What is the acyl enzyme
After step 3 when there’s now a c=o on the oxygen of the serine 195 and a amine group separated and free floating
What is step 4 of hydrolysis by chemotrypsin
The free floating amine part leaves
What is step 5 of hydrolysis by chemotrypsin
A second substrate of water is introduced and bind to the active site of the acyl enzyme
What is step 6 of hydrolysis by chemotrypsin
The his 57acts as a base again and deprotonated the water to gain a H
The new oh acts as a nucleophile and attacks the carbonyl of the acyl enzyme
Oxyanion hole stabilized the tetrahedral intermediate again
What is step 7 of hydrolysis by chemotrypsin
The tetrahedral intermediate is again collapsed by the bond between the ser 195s O and the carbon attached breaking
The ser 195s O takes a proton from the his 57 which is acting as an acid
What is step 8 of hydrolysis by chemotrypsin
The newly broken off R-COOH carboxylic acid is released and
What type of enzyme is chemotrypsin
Hydrolase because the peptide bond was broken by addition of water
