Lec 11 and 12: Enzymes I and II

Question 1

what is the function of the enzyme papain?

Answer 1

break any peptide

Question 2

what is the function of the digestive enzyme trypsin?

Answer 2

only splits bonds between lysine and arginine residues

Question 3

what is the function of the enzyme thrombin?

Answer 3

catalyses the hydrolysis or Arg- Gly only in a specific chain of residues

Question 4

what are the three major examples of proteolytic enzymes?

Answer 4

papain, trypsin, thrombin

Question 5

what are cyclins?

Answer 5

family of proteins that

control the progression of cells through the cell cycle by activating cyclin-dependent kinase (Cdk) enzymes.

Question 6

what is a cofactor?

Answer 6

non-protein chemical compound or metallic ion that is required for a protein’s biological activity to happen.

Question 7

what is an apoenzyme?

Answer 7

an enzyme without its cofactor

Question 8

what is a haloenzyme?

Answer 8

an enzyme with a cofactor q

Question 9

what are examples of cofactors?

Answer 9

Zn Cu,Fe

Question 10

how do cofactors affect an enzyme?

Answer 10

• Make it fold and create an active site
• Enhance the charge in the active site to improve substrate binding

Question 11

which cofactor does amylase require?

Answer 11

chloride ions

Question 12

what is a coenzyme?

Answer 12

Small organic molecules attach to activate the enzyme and detach when reaction completed to deactivate the enzyme

Question 13

what are examples of coenzymes?

Answer 13

vitamins such as niacin, riboflavin

Question 14

what are isozymes? (like isomers)

Answer 14

enzymes that differ in amino acid sequence but catalyse the same chemical reaction.

Question 15

how are isoenzymes different and what is their main role?

Answer 15

they display different kinetic parameters (e.g. different Km values), or different regulatory properties.

isozymes permits the fine-tuning of metabolism to meet the particular needs of a given tissue or developmental stage

Question 16

what enzyme is linked to hurler syndrome?

what does this disease cause?

Answer 16

defiency in iduronidase

hurler syndrome= abnormal bone structure and developmental delay

Question 17

In the hurler syndrome disease what are the types of severities?

Answer 17

Severe –> less severe

Hurler –> hurler scheie –> scheie

Question 18

which enzyme is linked to Niemann-Pick disease

what does the disease cause?

Answer 18

a lack in acid sphingomyelinase (ASM)

affects lysozymes

causes malfuncttion of major organ systems

Question 19

which enzyme is linked to Tay sachs disease?

what does the disease cause?

Answer 19

hexosaminidase-A that is absent from lysosymes

results in deterioration of nerve cells, mental and physical abilities

Question 20

which enzyme is linked to the disease homocystinuria

what does the disease cause?

Answer 20

Cystathionine beta-synthase

homocysteine amino acid and toxic by-products build up in the blood

bad eye sight, osteroporosis
(weakening of the bones)

Question 21

*NOTE* labelling an enzyme

Answer 21

Question 22

what are the 6 types of oxidoredcutases?

state what each one does

Answer 22

hydroxylases: add hydroxyl groups to subs (OH)
oxidases: intramolecular oxygen that accepts H/e-
peroxidases: reduction of H2O2
reductases: catalyse reductions
oxygenases: incoporate intramolecular oxygen into organic subs
dehydrogenases: oxidise substrate by transferring one or more hydride ion H-

Question 23

what is the function of transferases? given an example

Answer 23

that catalyse the movement of a functional group from one molecule to another. e.g methyl, phosphate, glycosyl grouyps

e.g human kinase

Question 24

what is the function of lyases?

what are the three types of lyases?

Answer 24

catalyse lysis reactions that generate a double bond.

1. carboxylases: add or remove COOH groups
2. aldohases: cleaved an aldol
3. dehydratases: remove oxygen or hydrogen in the form of H2O

Question 25

what is the function of isomerases enzymes?

Answer 25

catalyse structural changes within a molecule. only one substrate and one product with nothing gained or lost, so they represent only a change in shape.

Question 26

what is the function of ligases?

Answer 26

catalyses ligation: the joining of two substrates reaction is coupled to the hydrolysis of a disphosphate bond in ATP.

Question 27

what is the function of hydrolases? what is the difference between endo and exo enzymes?

Answer 27

Catalyse hydrolysis; the breaking of single bonds through the addition of water. endoenzymes cut in the middle of the chain whereas exo enzymes cut at the end of the chain to release an individual monomer.

Question 28

what are the three types of hydrolases enzymes?

Answer 28

Proteases/ peptidases: cleave peptide bonds between amino acids in order to breakdown proteins Lipases: break down lipids into fatty acids and glycerol by cleaving ester bonds Nucleases: cleave phosphodiester bonds between nucleotide subunits in nucleic acids

Question 29

what is the unit for enzyme activity?

Answer 29

μmol/min/mg of protein or IU/mg

Question 30

why is enzyme velocity measured at time 0?

Answer 30

prevents observed effects by feedback inhibition or reversible reactions

Question 31

what is the unit for the amount of enzyme which catalyses conversion of 1um of substrate per minute

Answer 31

1IU = 1μmol/min

Question 32

what is michaelis-menten enzyme kinetics?

Answer 32

The study of the rate of an enzyme controlled reaction (to see the effect of substrate concentration, of different inhibitors/drugs or different isozymes/mutations

Question 33

what is the michaelis-menton eqaution

Answer 33

Question 34

what is km used to ditinguish between?

Answer 34

isoenzymes

Question 35

what are the two types of reversible inhibition?

Answer 35

competitive and non-competitive

Question 36

what type of inhibitor is disulfiram antabuse?

Answer 36

a competitive inhibitor

Question 37

what is the antitode for methanol poisioning? how does this chemical work?

Answer 37

ethanol acts as a competitive inhibitor

Question 38

what type of inhibitor is nifediphine?

Answer 38

a non-competitive (allosteric) inhibitor prevents the uptake of calcium ions into cardiac cells to treat agina and high blood pressure

Question 39

what type of inhibition is shown in this lineweaver-burk plot?

Answer 39

competitive inhibition because Km is increased (substrate is more at 50%) but Vmax is unaffected (saturation point is still the same)

Question 40

what type of inhibtion is shown in this lineweaver-burk plot?

Answer 40

uncompetitive inhibition Km reduced Vmax is reduced

Question 41

what type of inhibition is shown in this lineweaver-burk plot?

Answer 41

Noncompetitive Km is unaffected (substrate level is still the same at 50% of Vmax) Vmax reduced (saturation point is lowe)

Question 42

what are Irreversible inhibitor give an example

Answer 42

substances that bind so tightly to the enzyme (by a covalent bond) that they cannot be removed e. g. Sarin binds to serine preventing nerve impiulse transmission e. g. aspirin reducing synthesis of inflammatory signals

Question 43

what is uncompetitive inhibition?

Answer 43

known as anti-competitive inhibition, takes place when an enzyme inhibitor binds only to the complex formed between the enzyme and the substrate (the E-S complex

Question 44

what type of inhibitor is lithium? what does it do?

Answer 44

lithium is an un-competitive inhibitor used to treat manic-depressive psychosis

Question 45

what is end product inhibition?

Answer 45

aka feedback inhibition where the reaction product inhibits the enzyme acitivity

Question 46

What does the inhibitor often bind to during feedback inhibition?

Answer 46

the allosteric site of the enzyme being inhibited

Question 47

what are zymogens?

Answer 47

any of a group of proteins that display no catalytic activity but are transformed within an organism into enzymes

Question 48

how does ELISA work?

Answer 48

ELISA: enzyme-linked immunosorbent assay 1. Primary antibody against antigen of interest is coated on 96well plate 2. Patient sample is added 3. Antigen binds to primary antibody 6. Washing removes unbound antigen 4. Secondary HRP conjugated antibody to antigen is added 5. Colour develops by adding HRP substrate

Question 49

why are 2 types of antibodies needed in indirect ELISA?

Answer 49

primary antibodies immobilise the antigen the secondary antibodies is used for the detection of the antigen