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Clin Sci: Biology sms1 > Lec 11 and 12: Enzymes I and II > Flashcards

Lec 11 and 12: Enzymes I and II Flashcards

1
Q

what is the function of the enzyme papain?

A

break any peptide

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2
Q

what is the function of the digestive enzyme trypsin?

A

only splits bonds between lysine and arginine residues

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3
Q

what is the function of the enzyme thrombin?

A

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

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4
Q

what are the three major examples of proteolytic enzymes?

A

papain, trypsin, thrombin

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5
Q

what are cyclins?

A

family of proteins that

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

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6
Q

what is a cofactor?

A

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

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7
Q

what is an apoenzyme?

A

an enzyme without its cofactor

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8
Q

what is a haloenzyme?

A

an enzyme with a cofactor q

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9
Q

what are examples of cofactors?

A

Zn Cu,Fe

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10
Q

how do cofactors affect an enzyme?

A
  • Make it fold and create an active site
  • Enhance the charge in the active site to improve substrate binding
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11
Q

which cofactor does amylase require?

A

chloride ions

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12
Q

what is a coenzyme?

A

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

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13
Q

what are examples of coenzymes?

A

vitamins such as niacin, riboflavin

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14
Q

what are isozymes? (like isomers)

A

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

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15
Q

how are isoenzymes different and what is their main role?

A

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

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16
Q

what enzyme is linked to hurler syndrome?

what does this disease cause?

A

defiency in iduronidase

hurler syndrome= abnormal bone structure and developmental delay

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17
Q

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

A

Severe –> less severe

Hurler –> hurler scheie –> scheie

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18
Q

which enzyme is linked to Niemann-Pick disease

what does the disease cause?

A

a lack in acid sphingomyelinase (ASM)

affects lysozymes

causes malfuncttion of major organ systems

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19
Q

which enzyme is linked to Tay sachs disease?

what does the disease cause?

A

hexosaminidase-A that is absent from lysosymes

results in deterioration of nerve cells, mental and physical abilities

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20
Q

which enzyme is linked to the disease homocystinuria

what does the disease cause?

A

Cystathionine beta-synthase

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

bad eye sight, osteroporosis
(weakening of the bones)

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21
Q

*NOTE* labelling an enzyme

A
22
Q

what are the 6 types of oxidoredcutases?

state what each one does

A

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-

23
Q

what is the function of transferases? given an example

A

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

e.g human kinase

24
Q

what is the function of lyases?

what are the three types of lyases?

A

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
25
Q

what is the function of isomerases enzymes?

A

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.

26
Q

what is the function of ligases?

A

catalyses ligation: the joining of two substrates

reaction is coupled to the hydrolysis of a disphosphate bond in ATP.

27
Q

what is the function of hydrolases?

what is the difference between endo and exo enzymes?

A

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.

28
Q

what are the three types of hydrolases enzymes?

A

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

29
Q

what is the unit for enzyme activity?

A

μmol/min/mg of protein

or

IU/mg

30
Q

why is enzyme velocity measured at time 0?

A

prevents observed effects by feedback inhibition or reversible reactions

31
Q

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

A

1IU = 1μmol/min

32
Q

what is michaelis-menten enzyme kinetics?

A

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

33
Q

what is the michaelis-menton eqaution

A
34
Q

what is km used to ditinguish between?

A

isoenzymes

35
Q

what are the two types of reversible inhibition?

A

competitive and non-competitive

36
Q

what type of inhibitor is disulfiram antabuse?

A

a competitive inhibitor

37
Q

what is the antitode for methanol poisioning?

how does this chemical work?

A

ethanol

acts as a competitive inhibitor

38
Q

what type of inhibitor is nifediphine?

A

a non-competitive (allosteric) inhibitor

prevents the uptake of calcium ions into cardiac cells to treat agina and high blood pressure

39
Q

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

A

competitive inhibition

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

40
Q

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

A

uncompetitive inhibition

Km reduced

Vmax is reduced

41
Q

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

A

Noncompetitive

Km is unaffected (substrate level is still the same at 50% of Vmax)

Vmax reduced (saturation point is lowe)

42
Q

what are Irreversible inhibitor

give an example

A

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

43
Q

what is uncompetitive inhibition?

A

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

44
Q

what type of inhibitor is lithium?

what does it do?

A

lithium is an un-competitive inhibitor

used to treat manic-depressive psychosis

45
Q

what is end product inhibition?

A

aka feedback inhibition

where the reaction product inhibits the enzyme acitivity

46
Q

What does the inhibitor often bind to during feedback inhibition?

A

the allosteric site of the enzyme being inhibited

47
Q

what are zymogens?

A

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

48
Q

how does ELISA work?

A

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
  4. Washing removes unbound antigen
  5. Secondary HRP conjugated antibody to antigen is added
  6. Colour develops by adding HRP substrate
49
Q

why are 2 types of antibodies needed in indirect ELISA?

A

primary antibodies immobilise the antigen

the secondary antibodies is used for the detection of the antigen

50
Q
A

Clin Sci: Biology sms1 (11 decks)

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