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Food Chem 2 > Enzymes > Flashcards

Enzymes Flashcards

1
Q

enzyme specificity
Absolute specificity

A

Protease -> protein
Lipase-> lipida

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2
Q

Group specificity

A

Enzyme act on a group of compounds

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3
Q

Stereospecificity

A

Enzyme that cat on optimal isomer

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4
Q

Race made and epimerase

A

Racemase- act on molecule with 1 chiral carbon

Epimerase - multiple chiral carbon

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5
Q

Enzyme purification is based on what

A

Size difference
Solubility diff
Charge diff
Selective absorption

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6
Q

Size diff is based on what

A

Dialysis
Ultrafiltration
Centrifugation
Gel filtration

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7
Q

Dialysis what is it and what is the problem

A

Enzyme is placed in a dyalisys bag and small molecule can diffuse bc of the small pores

Problems: every time there is an equilibrium dialysis cannot completely move the molecule

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8
Q

Ultrafiltration

A

Apply pressure in one side and force smaller molecule through membrane

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9
Q

Centrifugation

A

Larger molecules settle down faster

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10
Q

Gel filtration

A

Larger ones go down more quickly

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11
Q

Separation based on solubility is based on

A

Isoeletric preciptation
Salt fractionation
Solvent precepitation

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12
Q

Isoeletric preciptation

A

PH is adjust u t’il the net charge is neutral. PH ranges, diff enzymes have diff pIs and this is used to separate enzymes

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13
Q

Salt fractionation

A

Salts can alter charges on enzymes molecules
If you add salt more soluble

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14
Q

Solvent preciptation

A

Acetone or ethanol are used or decrease water activity you need to chill solvent to 0-4 degrés before adding the enzyme to prevent enzyme denaturation

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15
Q

Separation based on charge differences are based on

A

Ion exchange chromatography
Electrophoresis
Isolectric focusing

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16
Q

Ion exchange chromatography

A

Cation exchanger when + binds to -
Anion is the inverse

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17
Q

Electrophoresis

A

Based on size and charge
The larger the molecule the faster

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18
Q

Isoélectrique focusing

A

We genetate pH gradient in the gel by using ampholytes

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19
Q

Separation based on specific binding based on

A

affinity chromatography and hydrophobic interaction chromatography

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20
Q

Affinity chromatography

A

Ligand are bound to enzymes with resin

The principle of affinity chromatography is that the stationary phase consists of a support medium (e.g. cellulose beads) on which the substrate (or sometimes a coenzyme) has been bound covalently, in such a way that the reactive groups that are essential for enzyme binding are exposed. As the mixture of proteins is passed through the chromatography column, those proteins that have a binding site for the immobilised substrate will bind to the stationary phase, while all otter proteins will be eluted in the void volume of the column.

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21
Q

HIC: hydrophobic interaction chromatography

A

Bind hydrophobic material to enzymes after the unbound material are eluted and the bound material are next removed by pH change

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22
Q

Enzyme purity is tested by

A

Test for homeogeonity
Chromatographic behaviour
Active testing
Isolectric fusing

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23
Q

Test for homogeonity

A

Make sure is homogenous by electrophoresis. Serial band = pure

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24
Q

Chromatography behaviours

A

Take ans and get various peaks if they are symmetrical is oure

25
Q

Activity testing

A

Use diff substrates to know which enzyme is present. If it is more than one so it is not pure

26
Q

Put the enzyme groups in order

A

1) oxidoreductase
2) transferase
3) hydrolyse
4) lyase
5) isomerase
6) ligase
7) translocase

27
Q

True or false
Enzyme facilitate reactions by reducing energy barrier

A

True

28
Q

What is the effect of temperature on catalysis

A

The kinetic energy will increase until the optimum temperature after it will be degraded

29
Q

Effect of pH on catalysis

A

At externes pHs the enzyme will be denatured and there is an Ph optimum around ph 7

30
Q

What are the 3 types of enzyme inhibition

A

Competitive
Non competitive
Uncompetitive

31
Q

Competitive inhibition

A

The inhibitor will bind to the enzyme and take the place of the substrate. We can increase substrate concentration to overcome this problem

32
Q

Non competitive inhibition

A

The inhibitor will bind to another place on the enzyme and it cannot make products. It can overcome by doing dialysis or gel filtration to remove the inhibitors

33
Q

Uncompetitive inhibiton

A

The substrate will bind to the active site and it will open up another place so the inhibitor can bind.

34
Q

What is the beneficial aspects of food processing

A

Natural, non toxic
Specificity
They are effective under mild reactions
Not expensive
Easy to control

35
Q

What are some deleterious effects of food processing

A

Lipase/ phospholipase can cause hydrolysis of these compounds into free fatty acids that can form various oxidized compounds that can make off flavours

In canned foods if the caning process is not complete, the heat stable enzymes ( protease) may survive the canning and continue with protéolytique even during storage in the can

Cheeses proteins lysis can make bitter peptides and alter the taste

36
Q

What enzymes does cheese use and why

A

Enzymes will do the same function. The enzymes that can be presents are rennin, rennet, pepsin or chymosin

In cheese there is casiers bc of the mild. Enzyme can cleave the Phe(105)-met(106) peptide bond in the k-casein to enable curdling to happen. But when you add the enzyme they form a low molecular weight peptides that will remain in the solution that is whey

37
Q

What enzymes are found in winemaking and brewing and why

A

Amylase : break down carb to form glucose, the glucose is fermented by yeast and produce CO2 and alcohol

Protease : they are added to break down proteins in beverage into low molecular weight peptides and amino acids that remain in solution at refrigerated temperatures it will prevent precipitation of proteins

38
Q

What enzymes are used in baking and why

A

Amylase : breaks down starch into glucose that are fermented by yeast to make CO2 that enables the volume to swell

Lipase: produce volatile compounds

Lipoxidase : bleach the color of flour from yellow to white

39
Q

What are the enzymes used in meat industry and why

A

Protease : break down the large myofibrillar proteins to form low molecular weight peptides and free amino acids and it results in a more tender and modified taste

Lipase : flavor

40
Q

Enzymes can also be added to add smaller molecules into a buffer one in the fish meat industry. Which enzyme is it and why do we put it

A

Transglutamine ( TGAse) : they form isopeptide bond between NH2 groups in the side chain of lysine and glutamine.

The isopeptide bond are covalent bond because the products can be larger and though

41
Q

What are the chemical reactions in foods catalyses by

A

Proteases, carbohydrates and lipolytic enzymes ( hydrolases)

Chemical reaction if oxidoreductase

42
Q

I’m chemical reactions of protease there is 2 groups what is it and what they do
( endoprotease va exo)

A

1) endoprotease
Cleave provide bond randomly in the protein molecule
It impacts texture and solubilisation

2) exoprotease
Cleave peptide bond at the terminal protein and impact flavour

43
Q

What are the 2 groups of carbohydrase

A

Starch and cellular

Starch has an alpha 1-4 and alpha 1-6 linkages and cellulose has beta 1-4 linkage ( linear structure) and so cellulose can be more compacted than starch bc it is branched but it is more resistance to hydrolysis

44
Q

Is cellulose more resistant than starch

A

Yes because it can be more compacted because if it’s linkage ( alpha 1-4) because starche has a branched

45
Q

What is the most important function of lipase

A

Lipolysis bc it brings hydrology’s to the major fat ( triaglylcerides) to form glycerol and free fatty acids

46
Q

What lipolysis do

A

Texture and flavour changes
Texture bc of of the larger molecule becoming the free fatty acids and glycerol

Flavor bc of the oxidation of free amino acids

47
Q

Is lipase desirable or not

A

Depends on the food. It is not desirable in meats and fish but desirable in cheeses and chocolates

48
Q

What is the role of amino acid oxidase

A

Form Keto acids, ammonia and H2O2. It is made when a person doesn’t have a lot of carbs in the diet

49
Q

Role of PPOs ( polyphenol oxidase)

A

They catalyze the oxidation of phenolic compounds to form dark coloured compounds ( melanidins)

50
Q

Is melanoidin ( dark compounds ) desirable

A

Yes in chocolate tea coffe but not in Crustacea, vegetable

51
Q

Tile of glucose oxidase

A

Oxidation of glucose to form gluconic acid and H2O2

52
Q

Role of catalase and peroxydase

A

Breading of H2O2 to form less reactive H2O and O2
Catalase is specific for H2O2 and peroxidase for both

53
Q

Why catalase and peroxidase are important

A

Prevent oxidative damage

54
Q

What is the role of ça then oxidase

A

Catalase the hydroxylation of hypoxanthine to xanthine and xanthine is further oxidize and it will produce uric acid which is not good because it decreases the quality effects

55
Q

What are some examples of enzymatic modification of foodstuff

A

Change in solubility, functional properties and flavor changes

56
Q

What are some industrial application of proteases

A

1) removal of bitterness
2) modification of milk and whey proteins
3) hydrolysis of what gluten for use as flavoranys
4) modification of collagen and gelatin ( modified collagen )
5) alcoholic beverage
6) baking
7) recovery of scrap protein form offal bones and blood

57
Q

What are other less known application of enzymes

A

Removal of dental plaque with toothpaste containing des transes

Elimination of hair with keratinase

Solubilisation of cold tea solid with tanase

Synthesis of protein like molecule

58
Q

Methods for controlling enzymatic reactions in food

A

Traditional :
Based on temperature
Based on water activity
Based on chemicals

59
Q

What are the Nobel methods for controlling enzymatic reactions

A

High pressure treatments
Enzyme treatments ( killer enzyme)
Enzyme inhibitors ( inhibit protéolytique in fish flesh or meat prevent mushiness)
Chemical modification : side chains of enzymes molecules may be modified by attaching groups to modify the reactivities of the enzymes
Ionizing radiation : cause radiolysis of H2O molecules and the product of radiolysis of water can bind to the enzyme molecule and cause inhibition

Food Chem 2 (5 decks)

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