Enzyme activity

Enzymespecificity

Temperature

pH-Value

Inhibitingsubstances

(Zucker, Fett etc.)

MixingIntensity

WaterAktivity

Enzymeconcentration

Substrateconcentration

What are enzymes?

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Theoretically, an enzymatic reaction is reversible, i.e. the products can be reconverted into the original substances. However, the reaction equilibria do often not match in practice. E.g. a hydrolysis, hence the degradation of a molecule under water adsorpti-on, cannot be reversed in an aqueous environment, since the water released during the reverse reaction is confronted to a certain extent to the resistance of the ambient water and is pushed back into the substrate.

MechanismThe starting materials (educts and/or substrates) of an enzyme reaction are bound in the so-called active side of the enzyme, forming an enzyme-substrate complex. By a reduction of the binding energy in the substrate molecule, the enzyme enables the conver-sion into the reaction products, which the complex subsequently releases.

Enzymes are specific; they may oxidize and/or reduce, transfer, hydrolyze, separate, transform or generate. Enzymes are characterized by high substrate and reac-tion specificity, i.e. under numerous substances they select only the suitable substrates and catalyze exactly one of many conceivable reactions.

Enzymes are biocatalysts. They accelerate bioche-mical reactions by lowering the activation energy, which has to be overcome to allow metabolism. They are no living organisms, but relatively small, water-soluble proteins.

Enzymes are ubiquitous and occur in every cell of microbial, animal or plant life.

Structure example:Simplified protein structure of a fungal α-amylase

+ u u +

Reaction time

Activation energy(spontaneous reaction)

Activation energy(enzymatic catalysis)

Energy

Enzyme Substrate

Due to specificity, the general term “key lock princi-ple“ is used, i.e. a substrate fits an enzyme and/or an enzyme fits a substrate. Like all catalysts, the enzyme is again present in the starting form after the reaction.

OriginEnzymes are always of natural origin, namely animal, plant and, in most of the cases, microbial origin.Plant enzymes are mostly added as ingredients and/or extract to the food, e.g. the enzyme-active malt flour. They are obtained by germination and drying or extraction. Enzymes of microorganisms are won by fermentation or by cultivation on surfaces, and subse-quent extraction. More rarely used are enzymes from animal sources, an example is lysozyme from egg as preservative in hard cheese, or lab enzyme in cheese production.

In some cases, the origin of an enzyme has a strong influence on the characteristic. Thus, e.g. al-pha-amylase from a bacterium is different from alpha-amylase from fungi (see diagrams on pH and temperature dependence of the activity).

Factors of influenceHow fast an enzyme reaction runs off depends on many factors (see fig. Enzyme activity):It is important that all factors, which have an influence on the acti-vity, reach an optimum. A sudden total loss of activi-ty out of the optimal range is unusual.

pH fungal enzymesbacteria enzymes

0

20

40

60

80

100

2 3 4 5 6 7 8 9 10

0,00

0,05

0,10

0,15

0,20

0,25

0,30

0,35

0 1000 2000 3000 4000

Vmax

V 0,5 max

Km

s E

EE

E

EE

EE

s

s

s

ss

s

s s

ss s

s

s s

sss

s

s

s

Substrate concentrationE = enzymes S = substrate

Concentration and availability of the substrateThe concentration of the enzyme must as well be in the optimum range. If it is too low, the reaction rate is also low, as enzyme molecules are available only at few points of the system (e.g. a dough). If the con-centration is too high, the enzyme molecules block and do not optimally reach the substrate.

Enzyme classes:EC 1: Oxidoreductases

A- + B Ú A + B- [electrons] (e.g. metabolism)

EC 2: Transferases

A-X + B Ú A + B-X (e.g. transglutaminases)

EC 3: Hydrolases

A-B + H2O ÙÚ A-H + B-OH

(e.g. amylase, esterase, lactase, lipase etc.)

EC 4: Lyases

A-B Ú A+B (e.g. metabolism)

EC 5: Isomerases

A-B Ú B-A (often in medicine/DNA)

EC 6: Ligases

M1 + M2 + NTP Ú M1-M2 + NDP + P oder M1-M2 + NMP + 2P

(e.g. DNA)

Temperature (oC)

0

20

40

60

80

100

30 40 50 60 70 80 90 10020

fungal enzymesbacteria enzymes

If the substrate concentration is too high, it may come to an inhibition. Nevertheless, an inhibition can also be caused by other influences and/or other substances, e.g. by high salt concentrations.

Authors: Florian Paschen and Dr. Lutz Popper

Example temperature:

Example pH value:

Structure example: Simplified protein structure of a bacteria xylanase

Substrate changes the shapeduring the subtrate binding

Substrate

Product

Active Side

Substrate entersthe active side

Enzyme-Substrate-complex

Enzyme-Product-complex

Products disappear out of the enzyme, active side of the enzyme is free again

NO O

Animals

Farming

Fluids,e.g. milk

Plants

Cultivation

Disintegration

Aqueous extraction

Filtration/seperaton

Concentration

Drying

Standardization/blending

MicrobesYeasts, moulds, Bacteria

Firmentation

CellsTissue Tissue Fluids,e.g. rubber

Broth