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Bchem 393 > Classes Of Enzymes And Chemotrypsin > Flashcards

Classes Of Enzymes And Chemotrypsin Flashcards

1
Q

What is an ec number

A

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

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2
Q

What are the 7 enzyme classes

A

Oxidoreductase

Transferase

Hydrolase

Lyase

Isomerase

Ligase

Translocase

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3
Q

What does oxidoreductase do and what is an example of one

A

It does oxidation reduction reactions (transfers electrons)
Ex lactate dehydrogenase NAD+ to NAD

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4
Q

What does transferase do and what is an example of one

A

Transfers functional groups between molecules

Amino transferase

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5
Q

What does hydrolase do and what is an example of one

A
  1. Cleave molecules by addiction of water

Trypsin

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6
Q

What does lyase do and what is an example of one

A
  1. Adds atoms or functional groups to double bonds or removes them to form double bonds

Fumarase

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7
Q

What does isomerase do and what is an example of one

A
  1. Moves functional groups within one molecule

Proline racemase

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8
Q

What does ligase do and what is an example of one

A
  1. Joins two molecules together (powered by atp hydrolysis)

DNA ligase

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9
Q

What does translocase do and what is an example of one

A
  1. Catalyzes movement of ions or molecules across membranes or catalyzes their separation within membranes

Sodium potassium pump

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10
Q

Carbonic anhydrase is a

Hexokinase is a

A

Lyase

Transferase

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11
Q

What is chemotrypsin

A

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.

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12
Q

What amino acids do chemotrypsin cleave after

A

Phenylalanine, Methionine, tryptophan, isoleucine, tyrosine

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13
Q

What is the hydrophobic specificity pocket on chemotrypsin

A

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

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14
Q

What are the three aA in the catalytic triad

A

Asp 102

His 57

Ser 195

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15
Q

What does asp 102 do

A

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

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16
Q

What does his 57 do

A

Acts as a base to accept a proton from ser 195 to make it a nucleophile

17
Q

What does ser 195 do

A

The deprotonated oxygen on its side chain acts as a nucleophile

18
Q

What is step one of hydrolysisi by chemtrypsin

A

The substrate binds to the active site

19
Q

What is step 2 of hydrolysis by chemotrypsin

A

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

20
Q

How does the oxyanion hole stablize the negative tetrahedral intermediate

A

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

21
Q

What is step 3 of hydrolysis by chemotrypsin

A

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

22
Q

What is the acyl enzyme

A

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

23
Q

What is step 4 of hydrolysis by chemotrypsin

A

The free floating amine part leaves

24
Q

What is step 5 of hydrolysis by chemotrypsin

A

A second substrate of water is introduced and bind to the active site of the acyl enzyme

25
Q

What is step 6 of hydrolysis by chemotrypsin

A

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

26
Q

What is step 7 of hydrolysis by chemotrypsin

A

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

27
Q

What is step 8 of hydrolysis by chemotrypsin

A

The newly broken off R-COOH carboxylic acid is released and

28
Q

What type of enzyme is chemotrypsin

A

Hydrolase because the peptide bond was broken by addition of water

Bchem 393 (31 decks)

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